Rituximab‐induced late onset neutropenia in newly‐diagnosed B‐cell lymphoma correlates with Fc receptor FcγRIIIa 158(V/F) polymorphism
Authors: Szu‐Chin Li, Yi‐Chun Chen, Andrew M. Evens, Ching‐Chih Lee, Hui‐Fen Liao, Chi‐Chia Yu, Ya‐Ting Tung, Yu‐Chieh Su
Journal: American Journal of Hematology (2010)

Rituximab is a commonly utilized treatment agent for B-cell lymphoma. Late onset neutropenia (LON) has been identified as a complication associated with rituximab, primarily in conjunction with hematopoietic stem cell transplantation (HSCT). Scant data exists regarding rituximab-related LON outside the spectrum of HSCT, including newly-diagnosed lymphoma. We examined a large cohort of newly-diagnosed B-cell lymphoma patients treated with rituximab-based therapy. We identified patients with LON and analyzed the characteristics and outcomes. Furthermore, we utilized multiplex PCR for the detection of the FcγRIIIa 158 V/F polymorphism and correlated this with LON. Eighty consecutive B-cell lymphoma patients were examined. Nine of 80 (11.3%) patients developed LON. The clinical course of LON was generally self-limiting without adverse events. The onset of LON occurred at a mean of 66 days after the last course of treatment, while the mean duration of LON was 97 days. Moreover, the V/V and V/F polymorphisms were significantly associated with the occurrence of LON (P = 0.046) yielding an odds ratio for the development of LON of 1.47 (95% CI 1.21–1.78). We identified an incidence of LON following frontline rituximab-based treatment of 11.3%. The FcγRIIIa polymorphism was highly associated with development of LON. Rituximab is a commonly used treatment for B-cell lymphomas, either alone or combined with chemotherapy. Late-onset neutropenia (LON), occurring at least 4 weeks after cessation of therapy, is a recognized, late complication of rituximab-based therapy. The incidence of LON has been reported to range from 5.6% to 27.3% [1-7]. The vast majority of data regarding rituximab-related LON has been derived from patients undergoing hematopoietic stem cell transplantation (HSCT). In addition, predisposing features and pathogenic mechanisms remain poorly defined. Immunoglobulin G (IgG) Fc receptor (FcR) polymorphisms that influence the binding of IgG have been described [8-10]. Weng et al. reported that the high affinity FcγRIIIa 158 V allele is associated with rituximab-induced LON after autologous HSCT [11]. Indeed, the FcγRIIIa polymorphism may serve as a tool to identify a population at increased risk for developing neutropenia after rituximab therapy. However, to our knowledge, the association of the FcγRIIIa polymorphism in patients receiving rituximab therapy outside of HSCT has not been reported. We report here the incidence and clinical course of LON in a cohort of 80 newly diagnosed B-cell lymphoma patients who were consecutively treated with rituximab-containing chemotherapy (without HSCT). The study was conducted with the approval of human research ethics committees of our institution. We also examined the association of the FcγRIIIa 158 V/F polymorphism and rituximab-induced LON. The characteristics of patients enrolled in this study are shown in Table I. Of the 80 patients treated with rituximab-based chemotherapy, 9 (11.3%) developed LON. For the nine LON patients, the median follow up time was 37 months (range, 4–84 months). The onset of LON was between 30 and 138 days after cessation of rituximab-based therapy (mean 66 days). Patients experienced neutrophil recovery between 7 and 329 days (mean, 97 days) after onset. The nadir ANC ranged from 210 × 109/L to 1240 × 109/L (mean, 780 × 109/L); (Table II). With respect to LON-related complications, none of the patients experienced a serious adverse event including no episodes of neutropenia-related infections. The hemoglobin level and platelet count remained in the normal range during the entire course of LON. The clinical course was self-limited, and all patients achieved a full recovery of the ANC without administration of any granulocyte-colony stimulating factors. The overall survival was not different in patients who developed LON compared with the non-LON group (P = 0.80). All patients who developed LON had diffuse large B cell lymphoma, but this was not significantly different compared with the non-LON group (P = 0.24). Many other clinical factors were analyzed for potential association with LON. We were unable to demonstrate any associations with LON. Fivty-six blood specimens were available for evaluation of the FcγRIIIa 158 polymorphism. In the LON group, two patients had the V/V polymorphism, seven patients had the V/F polymorphism, while no patients had the FcγRIIIa 158 F/F polymorphism. In the non-LON group, two patients had the V/V polymorphism, 30 patients had the V/F polymorphism, and 15 patients had the FcγRIIIa 158 F/F polymorphism (Table III). Since the sample size was too small for comparison, we combined the VV/VF group together and compared with F/F group. Patients with VV/VF had a significantly increased rate of LON compared with the F/F group (P = 0.046). The odds ratio for VV/VF patients to develop LON was 1.47 (95% confidence interval, 1.21–1.78). Due to the absence of well-controlled studies, the natural history and incidence of LON has not yet been adequately defined. The manufacturer of rituximab, Genentech, has stated that LON is a rare condition, with a post-marketing reporting rate of 0.02% (in >300,000 patients) in 2002 [5]; however, there is likely a degree of under reported, especially since LON has typically been a self-limiting phenomenon. Specifically, the incidence of LON has been reported to range from 5.6% to 27.3% [1, 4, 6, 7, 12-14] in separate series. Of note, the vast majority of these studies included patients who received high-dose chemotherapy and allogeneic or autologous HSCT. The incidence of LON in the current study of patients with untreated B-cell lymphoma was 11.3% (9 of 80 patients). The definition of rituximab-associated LON has also varied form study-to-study. We utilized a strict definition of LON including exclusion of patients who had bone marrow involvement at diagnosis. Thus, it is not surprising that the incidence of LON was lower than most other reports. Interestingly, patients who have received rituximab for autoimmune disease have been reported to have a lower incidence of LON [15]. Rios-Fernandez noted only 1 in 23 autoimmune patients treated with rituximab developed LON [16]. In our series, the clinical course of LON was generally self-limiting. None of the patients required supportive therapy (including granulocyte-colony stimulating factor) or hospitalization, and none of the patients experienced infectious complications. The majority of previous reports have shown similar results [1, 4, 6, 13]. Some reports have shown that LON may progress to a more protracted and severe neutropenia in a minority of cases predisposing patients to serious infectious complications [12, 14]. In terms of timing, most series have shown that the onset occurs between 80 and 100 days [1, 5, 6, 12]. In our series, LON appeared to have a slightly shorter time of onset (mean, 66 days), which may reflect our follow-up policy. After the last course of chemotherapy, we arranged for patients to return to have routine complete blood counts every 2 weeks. This practice may have incorporated some lead-time bias resulting in the identification of an earlier time-to-diagnosis from last rituximab of LON. With respect to the duration of LON, it appeared slightly longer (mean, 97 days) compared with previous reports (15–56 days) [1, 12, 17]. There are several factors that may explain the longer recovery time; in addtion, to an "earlier" diagnosed as mentioned above, our clinical policy is to not routinely administer granulocyte-colony stimulating factors. In fact, none of our patients required granulocyte-colony stimulating factors support and all of who recovered without infection or other serious adverse event. We did not indentify any clinical risk factors that predicted the development of LON. It was previously reported that radiotherapy and intensive chemotherapy may increase the risk for LON [1]. These were not pertinent factors here since most of our patients did not receive radiotherapy or intensive drug therapy. We also did not note a difference in survival between the LON and non-LON groups, which is not surprising giving the self-limited nature of LON in our series. A larger series would be needed to confirm this finding. Weng et al. recently reported that the FcγRIIIa 158V allele dose was associated with an increased incidence of rituximab-induced LON [11]. Of note, their series included only patients with LON after autologous HSCT. Using a simple PCR method, we were able to confirm the FcγRIIIa 158 F/V polymorphism in our patient population of newly-diagnosed patients treated with frontline rituximab-based therapy. None of the patients here with LON were F/F. The pharmacokinetics of rituximab may be different in patients with the high affinity FcγRIIIa 158 V allele. In patients with the high-affinity V/V genotype, B lymphocyte depletion may be more profound, which subsequently stimulates increased bone marrow lymphopoiesis resulting in less effective granulopoiesis. This hypothesis is supported in part by the unusually high serum B-cell activating factor (BAFF) level that has been detected at the time of rituximab-induced neutropenia [18]. In conclusion, we documented a rate of rituximab-related LON of 11.5% among a large cohort of newly diagnosed B-cell lymphoma patients. The clinical course of LON was self-limited. We suggest that clinical follow-up of patients without empiric granulocyte-colony stimulating factor may be considered for patients with LON after rituximab-based therapy. Furthermore, the FcγRIIIa 158 V/V and V/F polymorphism was significantly associated with development of rituximab-related LON in newly-diagnosed B-cell lymphoma. Between April 2003 and January 2009, 100 newly diagnosed B-cell lymphoma patients who received rituximab-based chemotherapy at a single hospital were included in this prospective study. Twenty patients had bone marrow involvement at diagnosis and thus were excluded. The study was approved by the Tzu Chi Dalin General Hospital Institutional Review Board (IRB). The inclusion criteria for LON included: (1) an absolute neutrophil count (ANC) <1500/ul, (2) neutropenia occurring >4 weeks after last the rituximab-based treatment, and (3) bone marrow biopsy (including flow cytometry revealed) without evidence of lymphoma. We excluded all patients with the following conditions: (1) bone marrow involvement at start of chemotherapy, (2) cirrhosis (hepatitis B- or C related), (3) neutropenia (<1500/ul) before 1st cycle of chemotherapy, (4) use of concurrent medications that may cause neutropenia. All patients after completion of frontline therapy had complete blood counts followed every 2 to 3 weeks through 6 months. Further patients who developed LON continued close follow-up in the outpatient clinic (1 visit every 1–2 weeks) and a complete blood count was checked every 2 weeks until full neutrophil recovery. Heparin anti-coagulated blood samples were collected from all of the patients with informed consent. Genomic DNA was extracted from peripheral blood mononuclear cells using a DNA extraction kit. A polymerase chain reaction (PCR)-based method to determine FcRIIIa genotypes was used, as previously described [19]. The mean values and standard deviations were calculated to describe the data population. Pearson's chi-square test was used to evaluate the distribution of the three genotypes between each group. Statistical analyses were performed using the Fisher exact test or two-tailed t-test. Multiple clinical factors (gender, age, history of hepatitis C virus, history of hepatitis B virus, chemotherapy regimen, concurrent medications (e.g., anti-hypertensive or oral hypoglycemic agents), and lymphoma histology were evaluated in univariate and multivariate analyses using Cox proportional hazards regression for indicators of development of LON.