Antitumour antibiotic containing regimens for metastatic breast cancer

Abstract

Antitumour antibiotics are used in the management of metastatic breast cancer. Some of these agents have demonstrated higher tumour response rates than non-antitumour antibiotic regimens, however a survival benefit has not been established in this setting. To identify and review the randomised evidence comparing anti-tumour antibiotic containing chemotherapy regimens with regimens not containing an anti-tumour antibiotic in the management of women with metastatic breast cancer. The specialised register maintained by the Editorial Base of the Cochrane Breast Cancer Group was searched on 2nd May, 2003 using the codes for "advanced breast cancer" and "chemotherapy". Details of the search strategy and coding applied by the Group to create the register are described in the Group's module on The Cochrane Library. Randomised trials comparing anti-tumour antibiotic containing regimens with regimens not containing anti-tumour antibiotics in women with metastatic breast cancer. Data were collected from published trials. Studies were assessed for eligibility and quality, and data were extracted by two independent reviewers. Hazard ratios (HRs) were derived from time-to-event outcomes where possible, and a fixed effect model was used for meta-analysis. Response rates were analysed as dichotomous variables. Quality of life and toxicity data were extracted where present. A primary analysis was conducted for all trials and by class of antitumour antibiotic. Thirty-three trials reporting on 45 treatment comparisons were identified. All trials published results for tumour response and 26 trials published time-to-event data for overall survival. The observed 4084 deaths in 5284 randomised women did not demonstrate a statistically significant difference in survival between regimens that contained antitumour antibiotics and those that did not (HR 0.97, 95% CI 0.91 to 1.03, P = 0.35) and no significant heterogeneity. Antitumour antibiotic regimens were favourably associated with time-to-progression (HR 0.84, 95% CI 0.77 to 0.91) and tumour response rates (odds ratio (OR) 1.34, 95% CI 1.21 to 1.48) although statistically significant heterogeneity was observed for these outcomes. These associations were consistent when the analysis was restricted to the 29 trials that reported on anthracyclines. Patients receiving anthracycline-containing regimens were also more likely to experience toxic events compared to patients receiving non-antitumour antibiotic regimens. No statistically significant difference was observed in any outcome between mitoxantrone-containing and non-antitumour antibiotic-containing regimens. Compared to regimens without antitumour antibiotics, regimens that contained these agents showed a statistically significant advantage for tumour response and time to progression in women with metastatic breast cancer but were not associated with an improvement in overall survival. The favourable effect on tumour response and time to progression observed in anthracycline-containing regimens was also associated with greater toxicity.