Influence of precedent drug on the subsequent therapy in the sequence of trifluridine/tipiracil with/out bevacizumab and regorafenib for unresectable or recurrent colorectal cancer.

Background: Trifluridine/tipiracil (TFTD), with or without bevacizumab (Bev), and regorafenib are salvage chemotherapy options for metastatic colorectal cancer (mCRC). Here, we examined the influence of precedent drug on the efficacy of subsequent drug.

Method: The subjects were patients with mCRC who received salvage chemotherapy with TFTD (with/without Bev) followed by regorafenib (TFTD→Rego group/TFTD+Bev→Rego group), or reverse sequence (Rego→TFTD group) at the National Cancer Center Hospital between November 2013 and December 2020. The overall survival (OS), progression-free survival (PFS), disease control rate (DCR), tumor growth rate (TGR), and tumor growth kinetics (TGK) in the first evaluation were assessed in the three groups.

Results: A total of 69 patients, including 27 in the TFTD→Rego group, 13 in the TFTD+Bev→Rego group, and 29 in the Rego→TFTD group, were identified. There were no significant differences in the OS among the three groups, and in the PFS and DCR between the precedent and subsequent therapies in any of the groups. The median TGR (%/month) and TGK (mm/month) in the precedent→subsequent therapy were 50.9→32.7 (p = 0.044) and 8.76→7.79 in the TFTD→Rego group, 25.4→36.1 and 7.49→9.92 in the TFTD+Bev→Rego group, and 40.8→24.4 (p = 0.027) and 8.02→7.20 in the Rego→TFTD group, respectively.

Conclusion: In crossover use of TFTD with/without Bev and regorafenib, both agents showed similar efficacy in terms of the conventional parameters, but the differences observed in the TGR and TGK might suggest some influence of prior regorafenib treatment on the efficacy of subsequent TFTD therapy, and vice versa.