Role of adjuvant radiotherapy in resected T4aN0 colon cancer

For T4 colon cancer, multiple studies point to a benefit of adjuvant radiotherapy (RT). However, the evidence on whether and how adjuvant RT benefits survival outcomes in patients with T4aN0 disease is relatively scarce. This study sought to investigate the overall survival (OS) and colon cancer-specific survival (CSS) of patients with T4aN0 colon cancer defined by the American Joint Committee on Cancer (AJCC) 7th staging manual colon cancer treated with and without adjuvant RT, using the Surveillance, Epidemiology, and End Results (SEER) database. Patients aged over 20 years with T4aN0 disease defined by AJCC7th were eligible for inclusion. The propensity score matching (PSM) method was utilized to balance the baseline characteristics between those with and without adjuvant RT. Univariate and multivariable Cox regression analyses were conducted to determine the association between the study variables, OSS, and CCS, presented as hazard ratios (HRs) and 95% confidence intervals (CIs). Data of 3515 patients (with RT: 88; without RT: 3427) during 2010–2017 were extracted in the SEER*Stat database. After PSM, 440 patients (with RT: 88, without RT: 352) were included in the subsequent analyses. After controlled for relevant confounders including chemotherapy, the results showed that OS (adjusted HR [aHR] = 1.27, 95% CI = 0.81–1.78) and CSS (aHR = 1.54, 95% CI = 0.99–2.41) were not significantly different between patients who received adjuvant RT or not. In conclusion, no statistically significant difference in survival between patients treated with and without adjuvant radiation. Future studies evaluating the role of adjuvant RT for preventing recurrence in this specific patient subgroup are needed.