Lack of Benefit From Anti-EGFR Treatment in RAS and BRAF Wild-type Metastatic Colorectal Cancer With Mucinous Histology or Mucinous Component

Adenocarcinoma with mucinous histology or mucinous component are histologic subtypes of metastatic colorectal cancers (mCRCs) with limited benefit from cytotoxic agents. Their sensitivity to anti-epithelial growth factor receptors (EGFRs) is not clear. We retrospectively identified patients with RAS/BRAF wild type mCRC treated with anti-EGFRs. Our findings suggest no benefit from anti-EGFRs in mCRC with mucinous histology or mucinous component, irrespective of sidedness. Background: Adenocarcinoma with mucinous histology or mucinous component are histologic subtypes of metastatic colorectal cancers (mCRCs) with limited benefit from cytotoxic agents. Their sensitivity to anti-epithelial growth factor receptors (EGFRs) is not clear. Patients and Methods: The activity and efficacy of anti-EGFRs was retrospectively evaluated among patients with RAS and BRAF wild-type mCRC with or without mucinous histology or mucinous component. Subgroup analyses according to primary tumor location were conducted. Results: Overall, the study population included 22 mucinous or with mucinous component tumors (11 right- and 11 left-sided tumors) and 83 not mucinous tumors. One patient experienced partial response among mucinous tumors, whereas in the not mucinous group, 42 patients experienced partial response, with an overall response rate of 4% and 51%, respectively (P ¼ .003). The median progression-free survival was 2.8 versus 6.7 months (hazard ratio, 0.28; 95% confidence interval, 0.13-0.59; P < .001), and the median overall survival was 6.5 and 16.7 months (hazard ratio, 0.58; 95% confidence interval, 0.33-1.00; P ¼ .022), for the mucinous and not mucinous groups, respectively. Similar results were observed in subgroup analysis according to primary tumor location. Conclusion: Anti-EGFRs may not provide clinically meaningful benefit in mCRCs with mucinous histology or mucinous component compared with those without mucinous component, irrespective of sidedness.