Sparing lymph nodes during radiation may boost immune attack on rectal cancer

This phase 2 trial compares two treatment plans for people with locally advanced rectal cancer that is mismatch repair proficient (pMMR) or microsatellite stable (MSS). One group receives standard short-course radiation followed by chemotherapy. The other group receives a newer approach: radiation that spares the lymph nodes, followed by chemotherapy plus a PD-1 immune checkpoint inhibitor and bevacizumab, a drug that blocks blood vessel growth. The goal is to see if the newer combination leads to a higher rate of complete tumor disappearance before surgery or a watch-and-wait strategy.