The survival impact of palliative chemotherapy dose modifications on metastatic colon cancer

BACKGROUND: An uninterrupted dose of oxaliplatin-based cytotoxic therapy is an essential component in the standard treatment regimen of metastatic colon cancer (mCC). Data on the impacts of dose intensity reduction on the palliative treatment for patients with mCC remain scarce. Hence, this study aimed to investigate the impact of palliative chemotherapy dose modifications (DM) on the survival of patients with mCC. METHODS: Patients with stage IV colon cancer who received first-line palliative FOLFOX regimen chemotherapy between 2014 until 2018 in the Oncology Department of the National Cancer Institute were conveniently sampled retrospectively to analyse the treatment efficacy. The cumulative dose and duration of chemotherapy received by the patients were summarised as relative dose intensity (RDI) and stratified as High RDI (RDI ≥ 70%) or Low RDI (RDI < 70%). Progression-free survival (PFS) and 2-year overall survival (OS) between the two groups were analysed using Kaplan-Meier survival analysis and Cox proportional hazards models. RESULTS: Out of the 414 patients identified, 95 patients with mCC were eligible and included in the final analysis. About half of the patients (n = 47) completed the 12-cycle chemotherapy regimen and one patient received the complete (100%) RDI. The overall median RDI was 68.7%. The Low RDI group (n = 49) had a 1.5 times higher mortality risk than the High RDI group [OS, Hazard Ratio (HR) = 1.5, 95% Cl: 1.19–1.82] with a significant median OS difference (9.1 vs. 16.0 months, p < 0.01). Furthermore, patients with lower dose intensity showed double the risk of disease progression (PFS, HR = 2.0, 95% CI: 1.23–3.13) with a significant difference of 4.5 months of median PFS (p < 0.01). Gender and RDI were the independent prognostic factors of both OS and PFS. CONCLUSION: Reduction in the dose intensity of palliative chemotherapy may adversely affect both disease progression and overall survival among mCC patients.