Real-world retrospective study of neoadjuvant chemoradiotherapy with or without PD-1 inhibitor in locally advanced rectal cancer

PD-1 blockade benefits MSI-H/dMMR tumors after prior therapy. Its efficacy as first-line treatment for pMMR/MSS in locally advanced rectal cancer (LARC) remains unclear. A real-world retrospective cohort study at Lanzhou University (Gansu, China) compared outcomes of 84 LARC patients undergoing total mesorectal excision between 2021 and 2026. All patients received neoadjuvant chemoradiotherapy (nCRT). Patients were divided into Control (nCRT alone; n=59) and Combination (nCRT plus PD-1 inhibitor; n=25) groups. Baseline characteristics were balanced (all p>0.05). The Combination group showed a more favorable tumor regression (TRG) distribution than the Control group (Mann-Whitney U test, p=0.049), with higher pCR rates (32.0% versus 11.9%; p=0.041) and no TRG 3 cases (0.0% versus 8.5%). Sphincter preservation was numerically improved (Dixon rate 84.)% versus 64.4%; p=0.116). The combination arm also demonstrated rapid, uniform suppression of serum CEA and CA19-9. The authors conclude that adding PD-1 inhibitor to nCRT was associated with favorable outcomes among LARC patients. These preliminary results require validation in larger cohorts before informing clinical practice.