Moreover, the combination treatment resulted in a reduction of adverse reactions, including gastrointestinal reactions (RR = 0.52, 95% CI: 0.42–0.64, P < .00001), radiation proctitis (RR = 0.47, 95% CI: 0.33–0.68, P < .0001), myelosuppression (RR = 0.41, 95% CI: 0.26–0.64, P < .0001), as well as carcinoembryonic antigen (CEA) and squamous cell carcinoma antigen (SCC-Ag) levels. Here, CEACAM5 is linked to myelosuppression.