Capecitabine plus bevacizumab versus capecitabine in maintenance treatment for untreated characterised KRAS exon 2 wild-type metastatic colorectal cancer: a retrospective analysis in Chinese postmenopausal women

BACKGROUND: Capecitabine plus bevacizumab (CAP-B) maintenance treatment after 6 cycles of capecitabine, oxaliplatin, and bevacizumab (CAPOXB) has demonstrated clinical activity and failure to compromise quality of life in patients with metastatic colorectal cancer (MCC) in a previous phase 3 CAIRO3 study. The objective of this study is to evaluate the efficacy and safety of CAP-B versus CAP in maintenance treatment after 6-cycle CAPOXB induction therapy in Chinese postmenopausal women with untreated characterised KRAS exon 2 wild-type MCC. METHODS: During 2012–2016, prospectively maintained databases were reviewed to evaluate cohorts with untreated characterised KRAS exon 2 wild-type MCC and stable disease or better after 6-cycle CAPOXB induction treatment. After induction treatment, all patients received either CAP-B or capecitabine (CAP) as maintenance treatment. Median progression-free survival (mPFS) and median overall survival (mOS) were the primary endpoints. Safety was the secondary endpoint. RESULTS: A total of 263 women with untreated characterised KRAS exon 2 wild-type MCC and stable disease or better after 6-cycle CAPOXB induction treatment were included for the evaluation of efficacy and safety (CAP-B-treated cohort, n = 130 and CAP-treated cohort, n = 133). The mPFS was 11.5 months (95% confidence interval [CI], 5.6–17.4) and 9.2 months (95% CI, 3.6–14.8) for the CAP-B-treated and CAP-treated cohorts, respectively (HR 0.54, 95% CI 0.32~0.85; P = 0.013). The mOS was 16.2 months (95% CI, 11.4–18.7) and 12.4 months (95% CI, 10.6–15.5) for the CAP-B- and CAP-treated cohorts, respectively (HR 0.72, 95% CI 0.51~0.94; P = 0.022). The CAP-B-treated cohort experienced significantly more grade 3 or 4 diarrhoea (P < 0.001) than the CAP-treated cohort. CONCLUSIONS: CAP-B maintenance treatment after 6-cycle CAPOX-B in Chinese postmenopausal women with untreated KRAS exon 2 wild-type MCC is poorer tolerated but has a more modest, if any, benefit compared with that of CAP maintenance treatment.