Biological frailty and chemotherapy dose intensity independently predict survival in older adults with Stage II-III colon cancer.

PURPOSE: To evaluate the prognostic impact of chemotherapy dose intensity and frailty indices-including the laboratory-based Frailty Index (FI-Lab)-on survival in older adults with stage II-III colon cancer receiving adjuvant chemotherapy.

METHODS: This retrospective study included 94 patients aged ≥ 65 years with stage II (high-risk) or stage III colon cancer treated with adjuvant chemotherapy after curative surgery. Frailty was assessed using FI-Lab with a predefined cut-off of 0.25. Measures included the G8 geriatric screening tool, modified 5-item Frailty Index (mFI-5), and Charlson Comorbidity Index (CCI). Patients were categorised as optimal dose completed, optimal dose started with subsequent reduction, or not started at the optimal dose. Overall survival (OS) and disease-free survival (DFS) were analysed using Kaplan-Meier and Cox regression models.

RESULTS: With a median follow-up of 70 months, 28 recurrences (29.8%) and 22 deaths (23.4%) occurred. FI-Lab ≥ 0.25 independently predicted inferior OS (HR: 3.73; p = 0.023) and DFS (HR: 2.81; p = 0.029). G8, mFI-5, and CCI were not independently associated with survival. Dose initiation strategy was also independently associated with outcomes. Compared with the optimal dose completed group, patients not started at the optimal dose had worse OS (HR: 14.41; p = 0.011) and DFS (HR: 5.16; p = 0.013), whereas dose reduction after optimal initiation was not associated with survival.

CONCLUSIONS: Laboratory-based frailty and initial dose intensity independently predicted survival in older adults receiving adjuvant chemotherapy for colon cancer. These findings support individualised treatment strategies integrating biological reserve and early treatment intensity.