Background: Patients with refractory metastatic colorectal cancer (mCRC) rarely receive third-line or further treatment. In this context, regorafenib (R) and trifluridine/tipiracil (T) are two important novel therapeutic choices with statistically significant increases in overall survival (OS), progression-free survival (PFS), and disease control, with different toxicity profiles. This study is a subgroup analysis of our larger retrospective study, already published, whose objective was to assess the outcomes of patients when R and T were given sequentially. Patients and Methods: The study involved thirteen Italian cancer centers on a 10-year retrospective observation (2012-2022). In this subgroup analysis, we focused our attention on the correlation between the first drug treatment duration (<3 months, 3 to <6 months and ≥6 months) and survival outcomes in patients who had received the sequence regorafenib-to-trifluridine/tipiracil, or vice versa. Results: The initial study included 866 patients with mCRC who received sequential T/R, or R/T, or T or R alone. This analysis is focused on evaluating the impact of the duration of the first treatment in the sequence on clinical outcomes (OS, PFS) and includes 146 and 116 patients of the T/R and R/T sequences, respectively. Based on the duration of the first drug treatment, subgroups for the T/R sequence included 27 patients (18.4%) who received T for <3 months, 86 (58.9%) treated for 3 to <6 months, and 33 (22.6%) treated for ≥6 months; in the reverse sequence (R as the first drug), subgroups included 18 patients (15.5%) who received their first treatment for <3 months, 62 (53.4%) treated for 3 to <6 months, and 35 (31.0%) treated for ≥6 months. In patients who received their first drug treatment for a period of 3 to <6 months, the R/T sequence had a significantly longer median OS (13.7 vs. 10.8 months, p = 0.0069) and a longer median PFS (10.8 vs. 8.5 months, p = 0.0003) than the T/R group. There were no statistically significant differences between groups with first drug treatment durations of <3 months and ≥6 months. Conclusions: Our analysis seems to suggest that the administration of R for a period of 3 to <6 months before that of T can prolong both OS and PFS, as compared to the opposite sequence.
Keywords: first drug treatment duration; metastatic colorectal cancer; real-world study; regorafenib; sequential treatment; third-line therapy; trifluridine/tipiracil.