Abstract: We included eight RCTs involving 2156 participants with different stages of breast cancer and chemotherapy regimens. The trials were carried out between 1995 and 2008 and judged as being at least at moderate risk of bias. The strength of the evidence was weak for the majority of outcomes, which was mostly because of the small numbers of evaluable patients, varying definitions, as well as unclear measurements of the trials' outcomes and uncertain influences of supportive treatments on them. In most trials, the chemotherapy regimens had a risk of FN that was below the threshold at which current guidelines recommend routine primary prophylaxis with CSFs. Using CSFs significantly reduced the proportion of patients with FN (RR 0.27; 95% CI 0.11 to 0.70; number needed to treat for an additional beneficial outcome (NNTB) 12) but there was substantial heterogeneity which can be explained by possible differential effects of G-CSFs and GM-CSFs and different definitions of FN. A significant reduction in early mortality was observed in CSF-treated patients compared to placebo or no treatment (RR 0.32; 95% CI 0.13 to 0.77; NNTB 79). This finding was based on 23 fatal events in 2143 patients; wherein 19 of these 23 events occurred in one study and 17 events were attributed to progression of the disease by the study authors. For infection-related mortality, there were no significant differences between CSF and control groups (RR 0.14; 95% CI 0.02 to 1.29). In CSF-treated patients, the risk for hospitalization was significantly reduced (RR 0.14; 95% CI 0.06 to 0.30; NNTB 13), as well as the use of intravenous antibiotics (RR 0.35; 95% CI 0.22 to 0.55; NNTB 18). The risks of severe neutropenia, infection or not maintaining the scheduled dose of chemotherapy did not differ between CSF-treated and control groups. CSFs frequently led to bone pain (RR 5.88; 95% CI 2.54 to 13.60; number needed to treat for an additional harmful outcome (NNTH) 3) and injection-site reactions (RR 3.59; 95% CI 2.33 to 5.53; NNTH 3). In patients with breast cancer receiving chemotherapy, CSFs have shown evidence of beneﬁt in the prevention of FN. There is evidence, though less reliable, of a decrease of all-cause mortality during chemotherapy and a reduced need for hospital care. No reliable evidence was found for a reduction of infection-related mortality, a higher dose intensity of chemotherapy with CSFs or diminished rates of severe neutropenia and infections. The majority of adverse events reported from CSF use were bone pain and injection-site reactions but no conclusions could be drawn regarding late-term side effects.

Plain-language summary: This review included eight trials in which 2156 patients with breast cancer had randomly received CSFs or placebo or no treatment during chemotherapy. These trials were carried out between 1995 and 2008. Prophylactic treatment with CSFs significantly reduced the risk of developing FN by 73%. The estimated number of patients needed to be treated with CSFs in order to prevent one event of FN was 12. Although a significant decrease in mortality of all causes during chemotherapy and CSF therapy was noted, there was no reduction in infection-related mortality. There was no significant effect observed that planned chemotherapy schedules could be better maintained if CSFs were administered or that the number of patients with neutropenia decreased with CSFs. Notably, CSFs significantly reduced the need for hospital care yet frequently caused short-term adverse effects like bone pain and injection-site reactions. There were several limitations in this analysis: only a few trials could be included, the number of patients was low in many of these trials, and disease stages and chemotherapy treatments varied considerably. Moreover, the trial authors defined their outcomes differently, making comparisons across studies difficult. Information on the primary and secondary outcomes could not be obtained from all trials and the overall reporting quality was low. Many studies were dated and hence the administration of CSFs did not comply with current recommendations. Overall, CSFs have shown moderate evidence of beneﬁt in the prevention of FN in patients with breast cancer receiving chemotherapy. The evidence that the administration of CSFs could reduce early mortality of all causes was weak and substantiates the need of further studies. There was no reduction in risk of infection-related mortality with CSF treatment.