Addition of drug/s to a chemotherapy regimen for metastatic breast cancer

Background The addition of a chemotherapy drug or drugs to an established regimen is one method used to increase the dose and intensity of treatment for metastatic breast cancer. Objectives To assess the effects of adding one or more chemotherapy drugs to an established regimen in women with metastatic breast cancer. Search strategy We searched the Cochrane Breast Cancer Group's Specialised Register (to August 2009) using the codes for "advanced breast cancer" and "chemotherapy". This review is an update of the original Cochrane Review (Issue 3, 2006). Selection criteria Randomised trials with a first line regimen of at least two chemotherapy drugs compared to the same regimen plus the addition of one or more chemotherapy drugs in women with metastatic breast cancer. Data collection and analysis Two authors extracted data independently from published trials. We derived hazard ratios (HR) from time-to-event outcomes where possible, and used a fixed-effect model for meta-analysis. We analysed response rates as dichotomous variables and extracted toxicity data where available. Main results We identified 17 trials reporting on 22 treatment comparisons (2674 patients randomised). Fifteen trials (20 treatment comparisons) reported results for tumour response and 11 trials (14 treatment comparisons) published time-to-event data for overall survival. There were 1532 deaths in 2116 women randomised to trials of the addition of a drug to the regimen and control (the regimen alone). There was no detectable difference in overall survival between these patients, with an overall HR of 0.96 (95% confidence interval (CI) 0.87 to 1.07, P = 0.47) and no significant heterogeneity. We found no difference in time to progression between these regimens, with an overall HR of 0.93 (95% CI 0.81 to 1.07, P = 0.31) and no significant heterogeneity. Addition of a drug to the regimen was favourably associated with overall tumour response rates (odds ratio 1.21, 95% CI 1.01 to 1.44, P = 0.04) although we observed significant heterogeneity for this outcome across the trials. Where measured, acute toxicities such as alopecia, nausea and vomiting and leucopenia were more common with the addition of a drug. Authors' conclusions The addition of one or more drugs to the regimen shows a statistically significant advantage for tumour response in women with metastatic breast cancer but the results suggest no difference in survival time or time to progression. The positive effect on tumour response was also associated with increased toxicity.