Would you recommend adjuvant radiotherapy in addition to chemotherapy in gastric adenocarcinoma s/p gastrectomy with a distal positive resection margin?

This is one of the indications for adjuvant chemoRT for gastric cancer.

This patient is pT4a, pN2, R1/2 disease, and grade 3. They probably should have gotten peri-operative FLOT4, in which case the path would be ypT4a, ypN2, R1/2. Either way, the NCCN guidelines support the use of adjuvant radiation therapy for R1 disease, R2 disease, and R0 patients with high-risk features:

High-risk features include poorly differentiated or higher grade cancer, lymphovascular invasion (LVI), neural invasion, or <50 years of age, or patients who did not undergo D2 lymph node dissection.

Do we have a clinical trial looking at modern chemotherapy and adjuvant chemoRT for resection margin positive gastric cancer? No... but we should not necessarily constrain...