Does the efficacy of regorafenib differ in chemotherapy refractory metastatic colorectal cancer patients who had mucinous pathology compared to those who had non-mucinous pathology?

Purpose: To investigate the importance of mucinous histopathology on the assessment of tumor response in patients with metastatic colorectal cancer (mCRC) receiving regorafenib.

Materials And Method: All patients diagnosed with histologically confirmed mCRC in 2 oncology centers between 2013 and 2018 were retrospectively analyzed. Among 678 patients diagnosed with mCRC, 103 patients were treated with regorafenib. Ninety-four of these patients who had used at least 2 cycles of regorafenib and evaluable for treatment response were included in the analysis. Histopathologically, 18 patients with mucinous adenocarcinoma and 76 patients with nonmucinous adenocarcinoma were compared in terms of response rate and survival durations.

Results: Median follow-up duration of 6 months, median age of the patients was 61 (34-77) years. While 19.1% of the patients had mucinous histology, 80.9% had nonmucinous histology. The overall response rate was significantly lower in the mucinous subgroup than the nonmucinous subgroup (5.6% vs 43.4%, respectively, P = 0.003). Similarly, both progression-free survival (3.0 vs 4.0 months, respectively, P = 0.011) and overall survival duration were shorter in the mucinous subgroup (3.0 vs 7.0 months, P = 0.016, respectively) compared with the nonmucinous subgroup.

Conclusion: The histological subgroup may predict tumor response in mCRC patients receiving regorafenib. Its efficacy on nonmucinous histology had significantly more favorable than mucinous subtype.