Prognostic effect of radiotherapy on different colorectal cancer histological subtypes and tumor sites

Abstract

Abstract Background: The effect of radiotherapy (RT) may differ according to colorectal cancer (CRC) histological subtypes including adenocarcinoma, mucinous adenocarcinoma (MC), and signet-ring cell carcinoma (SR). This study analyzed the prognosis of three pathological CRC types and focused on RT's prognostic significance on three CRC histological subtypes. Methods: Patients diagnosed with adenocarcinoma (n=54,174), MC (n=3,813), and SR (n=664) in the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) database (2010–2017) were evaluated. Cox regression models and competitive risk models were built to assess the effect of RT on the risk of CRC-associated death. Results: Compared with adenocarcinoma patients, SR patients were associated with a 1.28-fold (HR=1.28, 95% CI: 1.16-1.42) risk of death. In the site-specific analyses, adenocarcinoma patients who received RT exhibited an increased risk of death (HR = 1.09, 95% CI: 1.03-1.15). RT did not show any prognostic influence for MC patients (HR = 0.96, 95% CI: 0.77-1.21). In SR patients. RT could reduce the risk of death (HR = 0.61, 95% CI: 0.39-0.95). After taking competing risk events (non-CRC-related death) into consideration. The results remained unchanged. Conclusions: Our study suggests that SR patients exhibited a worse OS (overall survival) than adenocarcinoma patients, and the effect of RT varied according to CRC histological subtypes.