Would you recommend adjuvant radiation therapy to a T4N0 colon cancer with invasion into other organs or the abdominal wall status post R1 resection?

Given the relative dearth of data for radiotherapy in the management of T4 colon cancer, one of my residents, Dr. Chris McLaughlin just completed and published a SEER database analysis on this population of patients (McLaughlin et al. Radiother Oncol 2019). He found that only about 5% of patients with T4 colon cancer had documented receipt of adjuvant radiation therapy, but that the benefit was very large as far as cause-specific survival (NNT=14). There was a greater absolute survival benefit f...

I do recommend post-operative RT with concurrent capecitabine for T4 tumors that invade the abdominal wall. I only cover the abdominal wall area at risk and treat to 50.4 Gy. For T4 tumors that invade other organs, I don't usually recommend radiation therapy except possibly in cases where the area at risk after an R1+ resection is visible on imaging using clips or CBCT. But you would have to weigh the benefit to the toxicity of radiating whatever organ was involved whether it be kidney, stomach,...

After an R1 resection of a T4 colon cancer, would not deliver postoperative chemo-radiation unless surgical clips had been placed to mark the area of positive margins and reconstruction had been performed to keep dose-limiting small bowel out of a post-op EBRT boost field. If clips were placed and reconstruction performed, would treat 45 Gy/25 fractions to an extended field based on preoperative imaging and 60-65 Gy to the clipped area plus narrow margin. If I were called to the OR for consultat...