Cuppone et al. Journal of Experimental & Clinical Cancer Research 2011, 30:54 http://www.jeccr.com/content/30/1/54 Page 2 of 9 treatment must necessarily be based to balance different aspects of patient characteristics, the disease characteris- tics and possible adjuvant treatment received (cumula- tive dose of anthracyclines, long-term toxic effects, possible administration of taxanes and/or trastuzumab) [4]. As a future perspective, the combination of clinical and molecular factors will guide the clinician in identify- ing the most effective therapy for a given patient, leaving more space and giving more importance to the molecu- lar characteristics of cancer [5,6]. Angiogenesis represents an important step in the pathogenesis, invasion, progression and development of metastatic phenotype of breast cancer and is regulated by pro-angiogenic factors such as vascular endothelial growth factor (VEGF)[7]. High expression levels of VEGF are associated with a poor prognosis and reduced survival in patients with breast cancer [8,9]. In this context, the theoretical block of tumor neo-vascularization be realized by monoclonal antibodies to factor soluble serum VEGF to its receptor or VEGFR (in different isoforms) or small molecules directed to the tyrosine-kinase receptor that appears to be a valid rationale for setting effective thera- pies [10]. Bevacizumab is a humanized anti-VEGF anti- body approved in combination with paclitaxel for first line treatment of advanced HER2-negative breast cancer. Although bevacizumab showed modest benefits as sin- gle agent, numerous preclinical studies have demon- strated synergy between anti-angiogenic therapy and chemotherapy [12]. The addition of Bevacizumab to chemotherapy in patients with HER-2 negative breast cancer is now one of the most viable treatment options, as the combination studies so far presented and pub- lished show that this association is able to increase the PFS and objective response [13-16]. In order to explore the magnitude of the benefit of add- ing Bevacizumab to chemotherapy for metastatic breast cancer with particular attention to safety, we conducted a meta-analysis. Methods The analysis was conducted following 4 steps: definition of the outcomes (definition of the question the analysis was designed to answer), definition of the trial selection criteria, definition of the search strategy, and a detailed description of the statistical methods used [17,18]. Outcome definition The combination of chemotherapy and Bevacizumab (Beva) was considered as the experimental arm and che- motherapy as the standard comparator. Analysis was conducted in order to find significant differences in pri- mary and secondary outcomes. Primary outcomes for the magnitude of the benefit analysis were both the Progres- sion Free Survival (PFS: time between randomization and progression or death from any cause) and the overall sur- vival (OS: time between randomization and death for any cause). Secondary end-points were: overall response rate (ORR), and grade 3-4 toxicities. Search strategy Deadline for trial publication and/or presentation was June 30th, 2010. Updates of Randomized Clinical Trials (RCTs) were gathered through Medline (PubMed: http://www.ncbi.nlm.nih.gov/PubMed), ASCO (Ameri- can Society of Clinical Oncology, http://www.asco.org), ESMO (European Society for Medical Oncology, http:// www.esmo.org), FECS (Federation of European Cancer Societies, http://www.fecs.be), and SABCS (San Antonio Breast Cancer Symposium, http://www.sabcs.org) web- site searches. Key-words used for searching were: advanced/metastatic breast cancer; chemotherapy; Beva- cizumab; randomized; randomized; meta-analysis; meta- regression; pooled analysis; phase III; comprehensive review, systematic review. In addition to computer browsing, review and original papers were also scanned in the reference section to look for missing trials. Furthermore, lectures at major meetings (ASCO, ESMO, ECCO, and SABCS) having ‘advanced or metastatic breast cancer’ as the topic were checked. No language restrictions were applied. Trial identification criteria All prospective phase III RCTs published in peer- reviewed journals or presented at the ASCO, ECCO, ESMO and ASTRO meetings until June 2010, in which patients with advanced or metastatic breast cancer were prospectively randomized to chemotherapy with or without Bevacizumab were gathered, regardless of treat- ment lines. Data extraction Hazard Ratios (HR) for PFS and OS and the number of events for secondary end-points were extracted; the last trial’s available update was considered as the original source. All data were reviewed and separately computed by four investigators (F.Cu., E.B., I.S., and D.G.). Data synthesis HRs were extracted from each single trial for primary end- points [19,20], and the log of relative risk ratio (RR) was estimated for secondary endpoints [21]; 95% Confidence Intervals (CI) were derived [22]. A random-effect model according to DerSimonian-Laird method was preferred to the fixed, given the known clinical heterogeneity of trials; a Q-statistic heterogeneity test was used. Absolute benefits for each outcome were calculated (i.e. absolute benefit = exp {HR or RR × log[control survival]} - control survival [23]; modified by Parmar and Machin [24]). The number