Platinum-containing regimens for metastatic breast cancer.

BACKGROUND: Studies have reported high tumour response rates for platinum-containing regimens in the treatment of women with metastatic breast cancer. Most of these studies were conducted prior to the 'intrinsic subtype' era, and did not specifically focus on metastatic triple-negative breast cancers (mTNBCs).

OBJECTIVES: To identify and review the evidence from randomised trials comparing platinum-containing chemotherapy regimens with regimens not containing platinum in the management of women with metastatic breast cancer.

SEARCH METHODS: For this review update, we searched the Cochrane Breast Cancer Group's Specialised Register, CENTRAL, MEDLINE, Embase, the World Health Organization's International Clinical Trials Registry Platform and ClinicalTrials.gov on 28 May 2015. We identified further potentially relevant studies from handsearching references of previous trials, systematic reviews, and meta-analyses. Prior to this review update, the most recent search for studies was conducted in May 2003 for the original 2004 review.

SELECTION CRITERIA: Randomised trials comparing platinum-containing chemotherapy regimens with regimens not containing platinum in women with metastatic breast cancer.

DATA COLLECTION AND ANALYSIS: At least two independent reviewers assessed studies for eligibility and quality, and extracted all relevant data from each study. Hazard ratios (HRs) were derived for time-to-event outcomes, where possible, and fixed-effect models were used for meta-analyses. Objective tumour response rates (OTRRs) and toxicities were analysed as binary (dichotomous) outcomes with risk ratios (RRs) used as measures of effects. Quality of life data were extracted where available. GRADE was used to rate the quality of evidence for survival and tumour response outcomes at the level of subgroups selected and unselected for mTNBC, and for toxicity outcomes based on combining data from selected and unselected populations.

MAIN RESULTS: This update includes 15 new eligible treatment-comparisons from 12 studies. In total, 28 treatment-comparisons, involving 4418 women, from 24 studies are now included in one or more meta-analyses. Of the 28 treatment-comparisons, 19 and 16 had published or provided extractable time-to-event data on overall survival (OS) or progression-free survival/time to progression (PFS/TTP), respectively. All 28 treatment-comparisons provided OTRR data that could be included in meta-analyses. Most women recruited to the studies were not selected on the basis of mTNBC status.In a subgroup of three treatment-comparisons assessing women with mTNBC, platinum-containing regimens may have provided a survival benefit (HR 0.75, 95% CI 0.57 to 1.00; low-quality evidence). In women unselected for intrinsic subtypes such as mTNBC, there was little or no effect on survival (HR 1.01, 95% CI 0.92 to 1.12; high-quality evidence). This effect was similar to the combined analysis of survival data for both populations (HR 0.98, 95% CI 0.89 to 1.07; I2 =39%, 1868 deaths, 2922 women; 19 trials). The difference in treatment effects between mTNBC women compared with unselected women was of borderline statistical significance (P = 0.05).Data from three treatment-comparisons with mTNBC participants showed that platinum regimens may improve PFS/TTP (HR 0.59, 95% CI 0.49 to 0.72; low-quality evidence). Thirteen treatment-comparisons of unselected metastatic participants showed that there was probably a small PFS/TTP benefit for platinum recipients, although the confidence interval included no difference (HR 0.92, 95% CI 0.84 to 1.01; moderate-quality evidence). Combined analysis of data from an estimated 1772 women who progressed or died out of 2136 women selected or unselected for mTNBC indicated that platinum-containing regimens improved PFS/TTP (HR 0.85, 95% CI 0.78 to 0.93). There was marked evidence of heterogeneity (P = 0.0004; I2 = 63%). The larger treatment benefit in mTNBC women compared with unselected women was statistically significant (P < 0.0001).There was low-quality evidence of better tumour response in both subgroups of women with mTNBC and unselected women (RR 1.33, 95% CI 1.13 to 1.56; RR 1.11, 95% CI 1.04 to 1.19, respectively). Combined analysis of both populations was closer to the effect in unselected women (RR 1.15, 95% CI 1.08 to 1.22; 4130 women). There was considerable evidence of heterogeneity (P < 0.0001; I2 = 64%), which may reflect between-study differences and general difficulties in assessing response, as well as the varying potencies of the comparators.Compared with women receiving non-platinum regimens: rates of grade 3 and 4 nausea/vomiting were probably higher among women receiving cisplatin- (RR 2.65, 95% CI 2.10 to 3.34; 1731 women; moderate-quality evidence) but the effect from carboplatin-containing regimens was less certain (RR 0.77, 95% CI 0.47 to 1.26; 1441 women; moderate-quality evidence); rates of grade 3 and 4 anaemia were higher among women receiving cisplatin- (RR 3.72, 95% CI 2.36 to 5.88; 1644 women; high-quality evidence) and carboplatin-containing regimens (RR 1.72, 95% CI 1.10 to 2.70; 1441 women; high-quality evidence); rates of grade 3 and 4 hair loss (RR 1.41, 95% CI 1.26 to 1.58; 1452 women; high-quality evidence) and leukopenia (RR 1.38, 95% CI 1.21 to 1.57; 3176 women; moderate-quality evidence) were higher among women receiving platinum-containing regimens (regardless of platinum agent).

AUTHORS' CONCLUSIONS: In women with metastatic breast cancer who do not have triple-negative disease, there is high-quality evidence of little or no survival benefit and excess toxicity from platinum-based regimens. There is preliminary low-quality evidence of a moderate survival benefit from platinum-based regimens for women with mTNBC. Further randomised trials of platinum-based regimens in this subpopulation of women with metastatic breast cancer are required.