Given the potential toxicities associated with alemtuzumab, and given the limited nature of the clinical trials testing its use in broad populations of patients with CLL, the use of alemtuzumab in patients with important co-morbidities may be associated with excessive risks. Currently, there are no published randomized controlled trials (RCTs) evaluating alemtuzumab alone or in combination with other chemotherapeutic agents for the treatment of relapsed or refractory CLL.  One RCT evaluated alemtuzumab administered to consolidate a complete or partial response to first-line fludarabine-containing chemotherapy in patients with CLL (1). The study was stopped early due to the occurrence of the National Cancer Institute Common Toxicity Criteria (NCI-CTC) Version 2.0 grade III/IV infection-related toxicity in seven of the first 11 patients randomized to the alemtuzumab arm. Patients in that arm had a significantly improved progression-free-survival (PFS) compared to observation (no progression versus  a mean PFS of 24.7 months, p=0.036).  Six single-arm studies evaluated disease response for alemtuzumab as a single agent in the treatment of patients with relapsed/refractory CLL post-fludarabine. The pooled overall response rate was 38% (complete response  6%, partial response  32%). Median time-to-progression was reported in three of those trials and ranged from four to 10 months.  Seventeen studies evaluated the toxicities associated with alemtuzumab as a single agent for the treatment of relapsed/refractory CLL: o Mild infusion-related side effects (e.g., grade I/II fever, rigors, vomiting, rash, dyspnea, and hypotension) were observed in most patients treated with intravenous alemtuzumab. Severe reactions (grade III/IV) were observed in up to 20% of patients treated with intravenous alemtuzumab; subcutaneous administration was rarely associated with severe infusion-related toxicity. o Thrombocytopenia and neutropenia (grade III/IV) were each observed in approximately one third of patients. o Infections were common (46% overall), often severe (18% grade III/IV), and included opportunistic, systemic viral, and invasive fungal diseases, despite antimicrobial prophylaxis. Cytomegalovirus (CMV) reactivation was commonly reported but effectively managed with adequate surveillance and treatment (usually intravenous ganciclovir); invasive CMV disease was rarely reported. Death due to infection occurred in approximately 4-5% of patients. Alemtuzumab is being compared to chlorambucil for first-line treatment of newly diagnosed patients with CLL in a large, multicentre, phase III RCT (2).  Alemtuzumab in combination with fludarabine is being compared to fludarabine alone for patients with relapsed CLL in a large, multicentre, phase III industry-sponsored study.  Alemtuzumab continues to be investigated in phase II studies as consolidation therapy for both newly diagnosed patients (fludarabine/rituximab/alemtuzumab) and patients with relapsed/refractory CLL (Pentostatin/cyclophosphamide/rituximab/alemtuzumab).# 
Is alemtuzumab a beneficial treatment option, with respect to outcomes such as survival, response rate, response duration, time-to-progression, and quality of life, for patients with Bcell chronic lymphocytic leukemia (CLL)? 2. What toxicities are associated with the use of alemtuzumab? 3. Which patients are more likely, or less likely, to benefit from treatment with alemtuzumab?

# Target Population
This evidence summary applies to adult patients with CLL.
- Treatment with alemtuzumab is a reasonable option for patients with progressive and symptomatic CLL that is refractory to both alkylator-based and fludarabine-based regimens.
Qualifying Statements  The evidence supporting treatment with alemtuzumab comes principally from case-series studies that evaluate disease response as the primary outcome measure. Patients should be informed that any possible beneficial effect of alemtuzumab on other outcome measures such as duration of response, quality of life, and overall survival are not supported in evidence and remain speculative at this time.  Treatment with alemtuzumab is associated with significant and potentially serious adverse treatment-related toxicities. Patients must be carefully informed of the uncertain balance between potential risks of harm and the chance for benefit reported in studies. Given the current substantial uncertainty in this balance, patient preferences will likely play a large role in determining the appropriate treatment choice. Is alemtuzumab a beneficial treatment option, with respect to outcomes such as survival, response rate, response duration, time-to-progression, and quality of life, for patients with B-cell chronic lymphocytic leukemia (CLL)? 2. What toxicities are associated with the use of alemtuzumab? 3. Which patients are more likely, or less likely, to benefit from treatment with alemtuzumab?

# CHOICE OF TOPIC AND RATIONALE
Chronic lymphocytic leukemia is the most common form of adult leukemia in the Western hemisphere, with an incidence rate of 4 out of 100,000; in patients over age 70, the incidence approaches 50 out of 100,000. Established diagnostic criteria allow CLL to be differentiated from related subtypes of indolent non-Hodgkin lymphomas (1). Patients requiring therapy are usually treated either with systemic alkylator-based chemotherapy or with a purine analogue (fludarabine). Unfortunately, CLL remains incurable with conventional chemotherapeutic approaches, and patients will relapse even after a favourable response to front-line therapy. Several randomized, controlled trials (RCTs) in patients with untreated, advanced stage CLL have documented superior response rates and response duration in patients randomized to fludarabine in comparison with alkylator-based chemotherapy (2)(3)(4). Despite those encouraging results, an improvement in overall survival has not been shown. Patients with disease refractory to standard chemotherapy have a particularly poor prognosis, and there is currently no accepted standard treatment. In order to improve outcomes for patients with CLL, new therapies and treatment approaches are needed.
Monoclonal antibodies are an emerging class of drugs with a unique mechanism of action that represents a novel approach to cancer treatment; rituximab, a humanized anti-CD 20 monoclonal antibody, has proven to be particularly effective for patients with B-cell lymphomas. Alemtuzumab, a humanized anti-CD52 monoclonal antibody, was the first of this class of drugs to receive U.S. Food and Drug Administration (FDA) approval for the treatment of patients with CLL relapsed or refractory to fludarabine; it is currently under review for approval in Canada. Although the function of CD52 is not known, this antigen is expressed on a variety of hematopoietic cells, including normal and malignant T-and B-lymphocytes; CD52 is not expressed on hematopoietic stem cells. Once bound to CD52, alemtuzumab induces cell death by one or more of three mechanisms: (i) complementdependent cellular cytotoxicity (CDCC), (ii) antibody-dependent cellular cytotoxicity (ADCC), and (iii) induction of apoptosis. Clinical activity has been demonstrated in heavily pre-treated patients, including those with disease progression following treatment with fludarabine. However, the benefits of alemtuzumab are offset by potential toxicities, including infection-related morbidity and mortality.
As licensing approval may precede the publication of phase III studies, the Hematology Disease Site Group (DSG) felt a systematic overview of the current literature was needed. This systematic review will inform further recommendations on this topic when updated with relevant, highquality evidence in the future.
This systematic review was developed by Cancer Care Ontario's Program in Evidence-based Care (PEBC). Evidence was selected and reviewed by one member of the PEBC Hematology DSG and methodologists.
This systematic review is a convenient and up-to-date source of the best available evidence on alemtuzumab in CLL. The body of evidence in this review is primarily comprised of mature RCT data, where available. This evidence is the basis for clinical recommendations developed by the Hematology DSG and presented in a practice guideline as part of this evidence-based series (Section 1). The systematic review and companion practice guideline are intended to promote evidencebased practice in Ontario, Canada. The PEBC is editorially independent of Cancer Care Ontario and the Ontario Ministry of Health and Long-Term Care.

# Literature Search Strategy
A systematic search of the published literature identified all reports relating to the use of alemtuzumab for the treatment of patients with CLL. The MEDLINE (1966  databases were searched according to the strategy shown in Appendix A. In addition, abstracts from the American Society of Hematology (ASH) (1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004) and the American Society of Clinical Oncology (ASCO) (1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005) annual conference proceedings were searched. Our search strategy included only studies published in English. Publications evaluating alemtuzumab in non-human subjects and those that were categorized as "published comments," "letters," and "editorials" were excluded. The United Kingdom Coordinating Committee on Cancer Research (UKCCCCR) Register, Physician Data Query (PDQ), National Institute of Health (NIH) Clinical Trials, and the European Organization for Research and Treatment of Cancer (EORTC) databases were searched to identify ongoing clinical trials. The National Guidelines Clearinghouse was searched for clinical practice guidelines. The references for each selected article were also reviewed. Where it was deemed necessary, the authors of included publications were contacted to obtain missing or additional data. It should be noted that a preliminary literature search was performed in November 2002 and subsequently updated in November 2004 and July 2005. After the preliminary literature search, the study selection criteria were amended to exclude studies with fewer than 20 evaluable patients. As a result, studies in the preliminary literature search that had fewer than 20 evaluable patients were later removed from the report. The data from those small studies, had they been included, would not have significantly affected the results or the DSG recommendations. For the sake of clarity, results from the preliminary and updated searches for this systematic review are presented together.

# Study Inclusion Criteria
Articles were selected for inclusion in this systematic review if they met the following criteria: 1. Studies included patients with CLL. 2. Studies tested the role of alemtuzumab as either induction or consolidation therapy, and either as a single agent or in combination with other therapy. 3. Results were reported for any of the following outcomes: survival, quality of life, time-toprogression, response duration, response rate, or adverse effects. 4. Trials had a minimum sample size of 20 evaluable patients.
Two independent observers reviewed the title and abstract of each citation. They were blinded to author name, institution, name of journal, nature of the paper (full paper or abstract), and results. The blinded observers scored each abstract as follows: "yes" if it met inclusion criteria, "no" if it did not meet inclusion criteria, or "maybe" if there was uncertainty. If both observers agreed that the abstract met the inclusion criteria, the complete document, if available, was retrieved for further analysis. In cases of disagreement, both observers reassessed the blinded abstracts together to achieve consensus. Where consensus could not be reached, or in cases where both observers gave a score of "maybe," the full document was retrieved and assessed by both reviewers to achieve consensus regarding eligibility. The reasons for excluding retrieved articles were documented.

# Synthesizing the Evidence
Due to a lack of adequately designed RCTs in our sample, a formal meta-analysis was deemed inappropriate. Where possible, response rates from single-arm studies evaluating similar patient groups were calculated. Data were pooled using intention-to-treat groups, and response proportions computed.

# Literature Search Results
A total of 527 citations were found with the original and updated searches; 40 citations met the inclusion criteria. Eighteen of the 40 citations were subsequently excluded from analysis for the following reasons:  One publication was a duplicate,  Three were anecdotal case reports (one report of severe immune thrombocytopenic purpura following a 10-week course of alemtuzumab, one report of gas gangrene six weeks after an eightweek course of alemtuzumab, and one report of a patient with CLL treated with three courses of alemtuzumab over a three-year period),  One evaluated patients with Sezary syndrome,  One evaluated non-clinical outcomes (T-cell subset recovery post-treatment with alemtuzumabthe clinical outcomes were reported in a separate publication that was included in this systematic review), and  Eleven were abstracts subsequently published as full papers (all met the inclusion criteria for this systematic review).
The 22 publications eligible for review (Table 1) are summarized below:  Nine single-arm studies (four full papers, five abstracts) evaluated alemtuzumab as a single agent in patients with relapsed or refractory CLL.  Three studies (two full papers, one abstract) evaluated alemtuzumab as a single agent in newly diagnosed patients with previously untreated CLL. One abstract publication reported only preliminary toxicity data from a RCT comparing alemtuzumab with chlorambucil as a first-line treatment of CLL.  Three single-arm studies (two full papers, one abstract) evaluated alemtuzumab in combination with additional agents for patients with refractory CLL.  Six studies (one full paper, five abstracts) evaluated alemtuzumab as consolidation therapy in CLL patients with a 'response' to previous-line therapy. One citation, published as a full paper, reported results from an RCT comparing alemtuzumab maintenance therapy to observation alone in patients with a response to first-line fludarabine. The trial was stopped early due to severe infection-related complications in patients randomized to the alemtuzumab arm. The remaining citations reported results from single-arm studies.  One publication reported a pooled analysis for the risk of cytomegalovirus (CMV) reactivation, CMV pneumonia, and CMV-related deaths in patients with lymphoid malignancies treated with alemtuzumab. 

# Practice Guidelines for CLL
Seven published practice guidelines on the management of CLL were retrieved. Two of those were excluded from our report because they were not published in English. The European Society for Medical Oncology (ESMO), the German CLL Study Group, and the Guidelines Working Group of the UK CLL Forum published separate guidelines for the diagnosis, staging, and treatment of patients with CLL that included reference to alemtuzumab therapy. One practice guideline was published specifically on the use of alemtuzumab in CLL by Keating et al. (2004).
The ESMO guideline did not include a description of the methods used to develop its recommendations; did not provide response rates, response durations, or associated toxicities of the studies included; and did not indicate explicitly which studies informed which recommendations.
The guideline published by German CLL group was described as a review article that stated it was a consensus document of the German CLL Study Group (with the membership listed). No description of the methods used to produce the guidelines were provided. Two studies on the outcomes of alemtuzumab therapy were cited as evidence for the German CLL group's recommendations, and were also retrieved in the literature search for our report (one was excluded because of our sample size criteria).
The UK CLL Forum guideline described the methods used to develop their recommendations and indicated explicitly which studies informed which recommendations. Outcome data, including response rates, durations of response, and median survival rates observed in trials were reported. Nine single-arm studies of alemtuzumab in patients with CLL informed their guideline. Of those studies, six are included in our report, and three were excluded in our search strategy because they did not meet our minimum sample-size criteria.
The practice guideline that addressed alemtuzumab use specifically indicated that it was developed out of an expert-opinion roundtable on the topic (held August 8-9, 2004). No description of methods are provided beyond that information. The Keating et al. guideline was informed by evidence from eight trials of alemtuzumab in CLL, all of which were included in our report.
The recommendations of these practice guidelines, which concern alemtuzumab use in patients with CLL, are addressed in the discussion.
Outcomes Question 1: Is alemtuzumab a beneficial treatment option, with respect to outcomes such as survival, response rate, response duration, time-to-progression, and quality of life, for patients with B-cell chronic lymphocytic leukemia? For this question, no studies reported quality-of-life outcome data.

# (i) Single agent alemtuzumab for relapsed/refractory CLL Response Rates
The overall response (RR), complete response (CR), and partial response (PR) rates associated with single-agent alemtuzumab for patients with relapsed or refractory CLL are summarized in Table 2 and include data from nine single-arm studies; there were no comparative or randomized studies available for analysis. Six trials each evaluated a standard 12-week course of alemtuzumab in patients with relapsed or refractory disease post-fludarabine therapy (5)(6)(7)(8)(9)(10). The combined RR rate across those six trials was 38% (range 31-41%); combined CR and PR rates were 6% (range 1-10%) and 32% (range 26-38%), respectively. One study (8) evaluated alemtuzumab administered subcutaneously and reported RR and CR rates similar to studies with intravenous administration; no trials directly compared subcutaneous with intravenous administration.
Three studies administered alemtuzumab for longer than 12 weeks. A single-arm study by Moreton et al. (11) evaluated the treatment with alemtuzumab until a maximal clinical response was achieved in patients with relapsed or refractory disease post-fludarabine therapy. RR, CR, and PR rates of 54%, 35%, and 19%, respectively, were reported for 91 patients treated for a median of nine weeks (range 1-16 weeks). Peripheral blood and bone marrow samples were obtained from all patients before, during, and after alemtuzumab therapy to evaluate minimal residual disease (MRD) status. A highly sensitive and validated four-colour flow cytometry-based assay was used to define MRD status; the limit of detection for that assay was approximately one CLL cell in 104 to 105 leukocytes (12). Twenty percent of patients achieved an MRD-negative remission in the bone marrow and peripheral blood. However, those patients had a median treatment-free period, prior to initiating alemtuzumab, of 10 months (range 4-43 months), and most patients (72%) had no evidence of lymphadenopathy or splenomegaly prior to alemtuzumab treatment. No trials have directly compared different alemtuzumab regimens.
The remaining two studies (13,14) administered therapy to 16 and 30 weeks, respectively, had smaller sample sizes (24 and 27 patients), and reported response rates similar to the other studies in that group.  1 Unless indicated otherwise, intervention was 30 mg Alemtuzumab administered intravenously three times per week for 12 weeks. 2 Evaluable patients are given in parenthesis, if less than total number of patients. 3 Only 3 patients received prior treatment (fludarabine). 4 Complete remission not reached in MRD-ve pts. Numbers are for MRD+ve patients with complete remission. 5 Regimen details not reported. 6 Alemtuzumab administered intravenously bi-weekly for 8 weeks + rituximab (375mg/m 2 administered weekly for 4 weeks. 

# Response Duration
Data on median time-to-progression (TTP) were reported in five single-arm studies evaluating alemtuzumab in patients with disease that had relapsed after or was refractory to fludarabine (Table 2) (5,6,8,11,13). Fludarabine-refractory disease was usually defined as either no response to fludarabine or relapse within six months following a response to fludarabine. The median TTP ranged from four to 10 months.
Moreton et al. ( 11) compared the median treatment-free-survival (TFS) according to the response to alemtuzumab (MRD-negative CR, MRD-positive CR, PR, or non-responders). Patients achieving MRD-negative CR had a significantly prolonged TFS compared to MRD-positive CR, PR, or non-responders (median TFS not reached, 20 months, 13 months, and six months, respectively, p<0.0001). The median TFS for the entire cohort was not reported.
Survival data were reported in 4 single-arm studies evaluating alemtuzumab in patients with relapsed or refractory disease post-fludarabine (Table 2) (5,6,8,13). Median overall survival (OS) ranged from 8 months to more than 2 years.
Moreton et al. ( 11) compared OS according to response to alemtuzumab. Patients achieving MRD-negative CR had a significantly prolonged OS compared to MRD-positive CR, PR, or nonresponders (median OS not reached, 60 months, 70 months, and 15 months respectively, p<0.0007). Median OS for the entire cohort was not reported.

# (ii) Single-agent alemtuzumab for previously untreated CLL Response Rates
Two studies investigated the RR, CR, and PR rates associated with a trial of single-agent alemtuzumab for patients with previously untreated CLL (15,16). Lundin et al. (15) reported an RR rate of 87% for 38 evaluable patients treated with subcutaneous alemtuzumab for 18 weeks; the CR and PR rates were 19% and 68%, respectively. Most patients were at the advanced disease stage (69% Rai III/IV).

# Response Duration
In the trial by Lundin et al. (15), median time-to-treatment-failure (TTF) had not been reached at 18 months. In an update of that trial, reported in abstract form, median TTF in responders had not been reached at 35 months (16). No other trials reported data pertaining to response duration.
No studies reported OS rates associated with alemtuzumab therapy for previously untreated patients with CLL.

# (iii) Alemtuzumab in combination with additional agents for relapsed/refractory CLL Response Rates
Three single-arm studies evaluated alemtuzumab-containing combination regimens for the treatment of relapsed or refractory CLL (Table 2) (17)(18)(19). No trials directly compared different combination regimens. One trial (19) evaluated alemtuzumab in combination with fludarabine. Elter et al. (19) reported an RR rate of 83% for 36 evaluable patients; the CR and PR rates were 31% and 53%, respectively.
Faderl et al. (17) reported a 63% RR rate (6% CR, 57% PR) for 32 patients treated with alemtuzumab in combination with rituximab. Wierda et al. (18) evaluated a regimen consisting of cyclophosphamide, fludarabine, alemtuzumab, and rituximab administered over six 28-day cycles; the overall response rate was 52% (14% CR, 38% PR).

# Response Duration
Elter et al. (19) reported a median TTP of 13.0 months for the entire patient cohort; for patients who achieved a CR, median TTP was 21.9 months. No other studies reported data for response duration associated with alemtuzumab-containing combination regimens for patients with relapsed/refractory CLL.
Elter et al. (19) reported a median OS of 35.6 months; for patients who achieved CR, median OS was not reached. No other studies reported survival data.

# (iv) Alemtuzumab consolidation for patients with a response to previous-line therapy Response Rates
One RCT ( 20) and four single-arm studies (32,33,35,37) reported response rates for alemtuzumab consolidation therapy; results are summarized in Table 3. The German CLL Study Group (Wendtner et al.) published results from an open-label, multicentre, randomized phase III trial comparing 12 weeks of alemtuzumab consolidation with observation in patients achieving at least a PR following six cycles of first-line fludarabine-containing chemotherapy (20). The study's sample size of 90 patients was designed to have an 80% statistical power to detect a 25% improvement in progression-free survival (PFS) at two years. The trial was stopped after the accrual of 21 patients due to the occurrence of the National Cancer Institute Common Toxicity Criteria (NCI-CTC) Version 2.0 grade III/IV infections in seven of the first 11 patients randomized to alemtuzumab consolidation. Two of eleven patients (18%) randomized to alemtuzumab consolidation improved upon their response to first-line therapy; both patients achieved a PR following first-line fludarabine-containing chemotherapy and improved to CR following consolidation with alemtuzumab.
The four single-arm studies evaluating alemtuzumab-consolidation therapy were reported in abstract form only (21)(22)(23)(24). All studies evaluated a four-to eight-week course of alemtuzumab in patients who had stable disease (SD) or better following first-or second-line chemotherapy. Response to alemtuzumab consolidation was generally defined as an improvement in 'post-induction' response status according to National Cancer Institute-Working Group (NCI-WG) criteria. Overall, response status improved following alemtuzumab consolidation. Two studies (21,23) documented an MRD-negative remission status in 38% to 51% of patients, based on clonality of the IgH gene rearrangement by polymerase chain reaction (PCR) analysis of peripheral blood and/or bone marrow samples. Note: a = abstract; A = alemtuzumab; C = cyclophosphamide; chemo = chemotherapy; CR = complete remission; fl = first-line; mc = monoclonal; med = median; mo = median months; n = near; N = number; nr = no response; NR = not reported; OS = overall survival; pc = polyclonal; PR = partial remission; PR+ = partial remission or better; ref = reference; resp = response to; RR = response rate; SD+ = stable disease or better; TTP = time-to-progression; vs. = versus, w = with; wks = weeks.

# Response Duration
Two studies reported data for response duration associated with alemtuzumab consolidation following a response to first-or second-line chemotherapy (20,23). In the RCT published by the German CLL Study Group (20), no progression occurred in the 11 patients randomized to alemtuzumab consolidation compared with a 24.7 months mean PFS in the 10 patients randomized to observation (p=0.036). O'Brien et al. (23) reported a median TTP of greater than 24 months in patients who demonstrated a response to alemtuzumab consolidation.
Survival data associated with the use of alemtuzumab-consolidation therapy were reported in the RCT published by the German CLL Study Group (20); median OS had not been reached in either the alemtuzumab arm or the observation arm. No other studies reported survival data.

# Question 2: What toxicities are associated with the use of alemtuzumab?
Toxicities associated with the administration of alemtuzumab were reported in most studies (Table 4). The most common adverse events can be broadly grouped into: (i) infusion-related side effects, (ii) myelosuppression, and (iii) infection-related toxicities.  

# (i) Infusion-related side effects
Infusion-related side effects were reported in 17 studies (5)(6)(7)9,11,13,(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25). They occurred in most patients treated with intravenous alemtuzumab, were usually grade I/II in severity, and were manageable with appropriate supportive care. The prophylactic use of pre-medications was reported in about one third of the studies and usually consisted of orally administered acetaminophen and antihistamines; corticosteroids were generally reserved for more severe reactions. Grade III/IV fever, rigor, and nausea were reported in up to 20% of patients, while other serious infusion-related toxicities were less common. The incidence of infusion-related side effects was similar regardless of the population evaluated, tended to be higher and more severe with the first infusion, and improved with subsequent courses of treatment.
The subcutaneous administration of alemtuzumab was reported in three trials (8,15,21) and was generally much better tolerated compared to similar patients treated intravenously (Table 4). Grade I/II fever (68%) and local injection site reactions (88%) were reported; grade III/IV reactions of any kind were rarely reported ( 2% of patients) (15).

# (ii) Myelosuppression
Data regarding myelosuppression associated with the use of alemtuzumab were reported in 10 trials (6)(7)(8)(9)11,13,15,(18)(19)(20). Results for studies evaluating different disease populations were analyzed separately.
Grade III/IV myelosuppression was common in studies evaluating alemtuzumab monotherapy for patients with relapsed/refractory disease (6-9,11,13); the pooled estimates (range) for grade III/IV neutropenia, thrombocytopenia, and anemia were 39% (22-66%), 31% (23-46%), and 8% (0-28%), respectively. Similar rates of grade III/IV myelosuppression were reported for studies evaluating alemtuzumab in combination and maintenance/consolidation regimens. Data regarding the coadministration of hematopoietic growth factors were not well reported.

# (iii) Infection-related toxicity
Data regarding the incidence of infections in patients treated with alemtuzumab were reported in 21 publications (5)(6)(7)(8)(9)(10)(11)(13)(14)(15)(16)(17)(18)(19)(20)(22)(23)(24)(25)(26)(27). In 13 studies, antimicrobial prophylaxis was administered during alemtuzumab therapy; cotrimoxazole in combination with antiviral therapy (acyclovir, valacyclovir, famciclovir), for the prevention of pneumocystis carinii pneumonia (PCP) and herpes virus infections, respectively, were most frequently cited. For this systematic review, data relating to infection-related toxicity were analyzed and reported separately for different study populations.

# (a) Single agent alemtuzumab for relapsed/refractory CLL
Data pertaining to infection-related morbidity in that patient population were reported in eight studies (5)(6)(7)(8)(9)11,13,14). The per capita incidence of all infections ranged from 30 to 93 per 100 patients (46 per 100 patients across studies). The incidence of Grade III/IV infections was 7 to 36 per 100 patients (18 per 100 across), and infection-related mortality ranged from 0 to 10 per 100 patients (4.5 per 100 across). Grade III/IV infections included disseminated viral infections (e.g., Varicella zoster virus and herpes simplex virus, systemic candidal infections, mycobacterial reactivation, and invasive fungal infections (e.g., pulmonary aspergillosis, rhinocerebral mucormycosis, and cryptococcal meningitis/pneumonia). PCP was reported but generally occurred in patients not receiving prophylaxis.
The incidence of CMV reactivation was reported in seven of the above-mentioned trials (5-8,10,11,14) and ranged from 1% to 29% (9% across); CMV pneumonitis was reported in four patients (0.8% across). The actual risk of CMV reactivation in that patient population was not clear because most studies did not prospectively screen all patients.
Williams et al. (27) retrospectively reported pooled safety data-3.6% of patients experienced 'symptomatic' CMV reactivation, CMV pneumonitis (0.8%), and CMV related-deaths (0.2%) in 1,538 patients with lymphoid malignancies treated with alemtuzumab in five single-arm trials-the routine screening of all patients for CMV reactivation was not performed in those studies. Patients who developed CMV reactivation were usually treated with intravenous ganciclovir until evidence of viremia resolved. Ganciclovir therapy was highly effective for treating CMV reactivation, but, because ganciclovir-induced neutropenia was common, treatment with myeloid growth factors (G-CSF) was often co-administered.
Rates of adverse events ranged from 11 to 82% in those studies. Overall, alemtuzumab therapy was prematurely discontinued in approximately 20% of patients due to an adverse event, most often due to infection-related complications and/or myelosuppression.

# (b) Single-agent alemtuzumab for previously untreated CLL
In an RCT comparing alemtuzumab to chlorambucil for newly diagnosed patients with CLL, Hillmen et al. (25) reported a CMV-reactivation rate of 15% for all patients randomized to receive alemtuzumab. All patients with detectable CMV reactivation were treated with ganciclovir; no cases of CMV pneumonitis occurred. Other infection-related toxicities have not yet been reported. Lundin et al. (15) reported CMV reactivation in four (11%) patients treated with subcutaneous alemtuzumab. One case of PCP occurred in a patient not receiving prophylaxis. An update describing the long-term follow-up for that patient cohort documented one episode of symptomatic Epstein-Barr virus (EBV infection 21 months post-alemtuzumab therapy (16). No other serious infections occurred.

# (c) Alemtuzumab in combination with additional agents for relapsed/refractory CLL
Faderl et al. (17) documented infections in 52% of patients with lymphoid malignancies treated with alemtuzumab in combination with rituximab; CMV reactivation occurred in 27%. Infections in CLL patients were not reported separately. Elter (19) reported data on 36 patients treated with alemtuzumab in combination with fludarabine; fungal pneumonia (n=2), CMV reactivation (n=2), and one infection-related death (E. coli sepsis) were the only reported infection-related complications.
Wierda et al. (18) reported CMV reactivation in 24% of patients (n=21) treated with alemtuzumab in combination with cyclophosphamide, rituximab, and fludarabine.

# (d) Alemtuzumab consolidation for patients with a response to previous-line therapy
Wendtner et al. randomized patients with a response to first-line fludarabine containing chemotherapy to consolidation with alemtuzumab (30mg intravenously three times per week  for 12 weeks) or observation (20). Explicit stopping rules were determined a priori and included grade III/IV infections occurring in five of the first 10 patients accrued to the alemtuzumab arm. The study was stopped early due to severe infections in seven of 11 patients randomized to alemtuzumab consolidation. Grade III/IV infections included CMV reactivation (n=2), CMV pneumonitis (n=2), pulmonary aspergillosis and HSV/human herpes virus (HHV)-6 (n=1), pulmonary tuberculosis (n=1), and herpes zoster reactivation (n=1). An additional two patients developed grade II CMV reactivation. Overall, nine of 11 patients (82%) randomized to alemtuzumab consolidation discontinued therapy due to an adverse event (severe infection in five patients and severe myelosuppression in four patients).
Four additional single-arm studies reported infection-related toxicity for alemtuzumab consolidation therapy (22)(23)(24)26). CMV reactivation was common, occurring in 21-57% of patients; the one reported case of CMV pneumonitis (22) contributed to patient death. The studies evaluated either 10mg or 30mg doses of alemtuzumab administered over six to eight weeks; there was no apparent difference in the rate or severity of infections according to treatment regimen.

# Question 3: Which patients are more likely, or less likely, to benefit from treatment with alemtuzumab?
Statistical evaluations for independent predictors of response, response duration, or survival were not reported in any study included in this systematic review. However, several publications reported subgroup analyses and clinical observations for patients who were more or less likely to respond to alemtuzumab. Several authors noted that patients with lymphadenopathy, particularly bulky lymph nodes (> 5cm), were less likely to achieve a clinical response to alemtuzumab-containing therapy (5,9,11,13,15,20,23). Keating et al. (5) reported that patients less likely to respond included those with Rai stage IV disease, at least one lymph node greater than 5cm in diameter, or a World Health Organization (WHO) performance status of two. Moreton et al. (11) evaluated alemtuzumab monotherapy administered to maximal response in patients relapsed or refractory to fludarabine and reported that patients were significantly less likely to respond if they had lymph nodes larger than 5cm (p<0.0001), had received three or more previous lines of therapy (p=0.0005), or had a pre-treatment WHO performance status greater than one. The RCT published by the German CLL study group (20) failed to find a correlation between response status and age, disease stage, response to previous-line fludarabine-containing chemotherapy, cumulative alemtuzumab dose, duration of alemtuzumab therapy, IgH mutational status, or cytogenetic aberrations; however, the analysis was limited to only 11 patients, because the trial was stopped early due to excessive severe infections in the alemtuzumab-consolidation arm.
In its deliberations, the Hematology DSG places particular emphasis on the following: (a) results from published RCTs (where available), (b) the recognition of a hierarchy of outcomes that should influence treatment decisions, with priority given to therapies found to extend life or improve quality of life, and (c) the potential toxicities associated with treatment, with particular emphasis on those toxicities seen in the patients most likely to make up the eventual population treated. The members of the Hematology DSG had considerable difficulty reaching consensus on the appropriate wording of the recommendation for a potential indication for alemtuzumab in patients with CLL; the recommendation went through multiple iterations (see section 3, Guideline Development and External Review-Methods and Results). Based on their review of the evidence provided in this systematic review, the DSG considered several interpretations for the use of alemtuzumab in patients with CLL.
The DSG regards alemtuzumab as an active agent for the treatment of patients with relapsed or chemotherapy-refractory CLL. This conclusion is based on response data from single-arm studies that report partial responses in approximately one third of patients and recognizes that complete remissions are uncommon. From a perspective of drug and/or multi-agent regimen development, these data are extremely promising and warrant further testing of alemtuzumab.
In their deliberations, the DSG cited the following factors leading to the above recommendation: (a) a lack of data from properly designed RCTs, (b) a paucity of comparative data suggesting improved response duration, quality of life, or improved overall survival compared with alternative treatment approaches, and (c) significant potential toxicity, particularly infection-related morbidity and mortality. Given the anticipated toxicity, data from RCTs demonstrating improvement in clinically meaningful outcome measures (e.g., time-to-progression, quality of life, or overall survival) are required before recommendations permitting the routine use of alemtuzumab in this patient population can be made.
The practice guidelines published by ESMO ( 28) and the UK CLL Forum ( 29) made recommendations regarding the use of alemtuzumab in previously treated patients. The ESMO guideline recommended alemtuzumab as an option for patients with refractory disease following firstline therapy, based on the lowest level evidence (ASCO level V evidence: small case-series). In addition, the UK CLL Forum guideline recommended alemtuzumab for use in patients without bulky lymphadenopathy (<5cm), who were previously treated with alkylating agents and refractory to fludarabine. The evidence informing the UK CLL Forum recommendation was similar to the evidence contained in this report and was comprised of data from a smaller selection of single-arm studies. The German CLL Study Group determined that definitive recommendations could not be made regarding alemtuzumab use and indicated that further testing in clinical trials would be preferred (30). The Keating et al. guideline (31) did not make explicit recommendations regarding the appropriateness of alemtuzumab use in CLL patients, but implied that alemtuzumab is appropriate in fludarabinerefractory patients. Keating et al. also stated that advanced age should not be a contraindication for alemtuzumab use.
The DSG considered the above recommendations to be based on low levels of evidence and, initially, was not convinced that these recommendations would inform the basis of a best clinical practice. Instead, the DSG initially concluded that potential benefits (response rates in a minority of patients, uncertain benefit in terms of response duration, overall survival, and quality of life) were offset by the potential for significant toxicity. Therefore, an initial recommendation was developed to indicate that there were insufficient data to support the routine use of alemtuzumab in patients with CLL. The DSG acknowledged the potential controversy that could result from issuing a "nonpermissive" recommendation regarding alemtuzumab use and the potential implications such a recommendation might have for drug availability. The DSG was aware that its recommendations differed from those of other existing practice recommendations, including those published by ESMO and the UK CLL Forum.
The DSG was also aware that within the response data described from the literature reviewed were responses of a magnitude that reporting authors, and members of the DSG, considered to be clinically important. While the precise frequency of these responses were uncertain, and the best estimate was that they would be infrequent, the DSG acknowledged that an opportunity for such a response, even with substantial risks of toxicity, may be highly desired by some patients. The DSG attempted to reflect this sentiment by indicating that, after balancing the benefits and risks of treatment, certain patients may wish to consider a trial of therapy. While the DSG had concerns with issuing an unclear and potentially conflicting set of recommendations, it initially considered this option to represent the best available alternative and offered the following guidance: For patients with CLL, there is insufficient evidence to recommend the use of alemtuzumab outside of clinical trials. The DSG recognizes that, in highly selected cases, after thorough consideration of the risks and benefits, a trial of alemtuzumab might be considered. Section 3 details the subsequent Practitioner Feedback and notes that responding clinicians were generally in agreement with the synthesis and interpretation of the available literature and the resulting recommendation. However, a small number of respondents commented on the lack of clarity associated with the recommendations. As a result, the DSG continued its consensus process in an effort to develop a clearer statement and issued a new set of recommendations.
The redeveloped recommendation states, "Treatment with alemtuzumab is a reasonable option for patients with progressive and symptomatic CLL that is refractory to both alkylator-based and fludarabine-based regimens." In order to account for the continued concern about the level of evidence supporting this recommendation and the potential adverse risk-benefit profiles of this therapy, a detailed set of Qualifying Statements were also developed.

# ONGOING TRIALS
The NCI, UKCCCCR, PDQ, NIH Clinical Trials, and EORTC databases were searched for any ongoing clinical trials. Alemtuzumab in combination with fludarabine is being compared with fludarabine alone for patients with relapsed CLL in one large, multicentre, phase III industrysponsored study. Alemtuzumab continues to be investigated in phase II studies as consolidation therapy for both newly diagnosed patients (fludarabine/rituximab/alemtuzumab) and patients with relapsed/refractory CLL (Pentostatin/cyclophosphamide/rituximab/alemtuzumab). Alemtuzumab is also being compared with chlorambucil in a large, multicentre RCT of the first-line treatment of newly diagnosed patients with CLL (25).
Treatment with alemtuzumab is a reasonable option for patients with progressive and symptomatic CLL that is refractory to both alkylator-based and fludarabine-based regimens.
The evidence supporting treatment with alemtuzumab comes principally from case-series studies that evaluate disease response as the primary outcome measure. Patients should be informed that any possible beneficial effect of alemtuzumab on other outcome measures such as duration of response, quality of life, and overall survival are not supported in evidence and remain speculative at this time.
Treatment with alemtuzumab is associated with significant and potentially serious adverse treatment-related toxicities. Patients must be carefully informed of the uncertain balance between potential risks of harm and the chance for benefit reported in studies. Given the current substantial uncertainty in this balance, patient preferences will likely play a large role in determining the appropriate treatment choice.
Given the potential toxicities associated with alemtuzumab, and given the limited nature of the clinical trials testing its use in broad populations of patients with CLL, the use of alemtuzumab in patients with important co-morbidities may be associated with excessive risks. All work produced by the PEBC is editorially independent from its funding agencies.
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