First-line therapy of bevacizumab plus chemotherapy versus cetuximab plus chemotherapy for metastatic colorectal cancer patients with mucinous adenocarcinoma or mucinous component.

BACKGROUND To compare the efficacy of first-line bevacizumab plus chemotherapy with cetuximab plus chemotherapy based on the stratification of metastatic colorectal cancer (mCRC) patients with mucinous adenocarcinoma (MA) or mucinous component (MC). METHODS A retrospective study involving all mCRC patients receiving first-line bevacizumab-based or cetuximab-based chemotherapy at our hospital from September 2013 to January 2020 was conducted. Overall survival (OS), progression-free survival (PFS), and objective response rate (ORR) were compared between the cetuximab-chemotherapy group and the bevacizumab-chemotherapy group on the basis of the conventional pathological classification of MA or MC. RESULTS A total of 620 patients with mCRC were included in our study, consisting of 141 (22.7%) patients with MA/MC and 479 (77.3%) patients with non-mucinous adenocarcinoma (NMA). In the MA/MC cohort, patients who were treated with bevacizumab-based chemotherapy were associated with significantly better OS than those treated with cetuximab-base chemotherapy (30.0 vs. 26.3 months, p = 0.002), irrespective of tumor sites. The efficacy of bevacizumab-based chemotherapy was higher in nearly all subgroups as shown in the subgroup analysis. In the NMA cohort, median OS was better in the cetuximab plus chemotherapy group than that in the bevacizumab plus chemotherapy group (32.2 vs. 27.0 months, p = 0.005) for left-side mCRC patients, whereas OS was significantly longer in the bevacizumab plus chemotherapy group for right-side mCRC patients (26.0 vs. 20.9 months, p = 0.013). CONCLUSION Conventional pathological classification (e.g. MA/MC) should be considered when tailoring the individualized optimal treatment for mCRC. Bevacizumab plus chemotherapy as first-line therapy may be the optimal option for patients with MA/MC.