Short-term and long-term oncological outcomes of chemoradiotherapy for rectal cancer patients with or without oxaliplatin: a propensity score-matched retrospective analysis

Background/Aim: Current approaches for locally advanced rectal cancer (LARC) typically recommend neoadjuvant chemoradiotherapy (nCRT) with 5-fluorouracil (5FU) or its oral analogs followed by surgery as the standard of care. However, the question of whether intensifying concurrent chemotherapy by adding oxaliplatin to the 5FU-based backbone can yield better outcomes remains unresolved. This study aimed to investigate the benefits of incorporating oxaliplatin into fluoropyrimidine-based chemoradiotherapy (CRT) to increase locoregional control and survival. Methods Among 290 patients with LARC admitted to the Iran Cancer Institute's radiation oncology department between January 2008 and December 2019, 29 received CAPEOX (capecitabine 625 mg/m²/bid on RT days and weekly oxaliplatin 50 mg/m²), whereas 293 received capecitabine (825 mg/m² twice daily or rarely 5FU in the first 4 days and last week of radiotherapy (RT)). Variables potentially affecting treatment outcomes were used for propensity score matching. Kaplan‒Meier and log-rank tests were employed for overall survival (OS) and disease-free survival (DFS) analyses and were adjusted with propensity score matching. Results Data from 29 patients who received CAPEOX and 216 patients who received capecitabine were analyzed after propensity score matching without replacement. After propensity score matching, in the multivariate analysis, CAPEOX significantly increased the likelihood of achieving a pathologic complete response (pCR) by 4.38 times (CI: 1.90–10.08, p value < 0.001). However, CAPEOX did not demonstrate any statistically significant predictive value for DFS (P = 0.500) or OS (P = 0.449). Conclusion The addition of oxaliplatin resulted in a significantly higher rate of pCR without any translation into long-term survival outcomes.