In light of findings from GOG 258, is the benefit of adjuvant RT in IIIC endometrial cancer worth the potential acute and late risks of RT in the setting of significant autoimmune disease?

I agree with the thoughtful answers of others in terms of tailoring therapy and balancing risk/benefit. In this case, however, GOG 258 answered the value of doing radiation on top of chemotherapy for any patient that met its criteria. And in this case, it included 75% that indeed had stage IIIC disease. Adding radiation did not improve survival, period. Even with long-term follow-up as we saw at SGO 2023. So, regardless of individual risks related to RT toxicity, if your goal is survival, it adds no value to these patients. If you are specifically wanting to lower the risk of vaginal cuff recurrence you could add vaginal brachytherapy to her chemo, but per the study, you would need to treat 20 patients with radiation to prevent 1 vaginal re...

As in almost any case of endometrial cancer, the decision of what adjuvant therapy, if any, should be recommended is multi-factorial. The goal is to optimize the therapeutic ratio, which includes consideration of the chance of cure and/or local control as well as the risk of acute and late toxicities. In the case presented, there is very likely a higher risk of acute and late toxicities compared to most cases. Of course, these risks are present with both chemotherapy as well as RT. Given the 258 data and the information presented in the question, I would tend to favor the omission of RT in this case. However, there are probably some circumstances in which I might favor some form of RT (maybe true pelvis only to a lower dose, e.g. 40 Gy). In...

The patient requires chemotherapy at a minimum, which frequently helps to reduce immunosuppressant needs in autoimmune conditions.

If the patient was able to undergo RT afterwards without being on high dose (for RA) methotrexate, I would have a discussion of the pros/cons of pelvic RT in this scenario and perform shared decision-making with the patient. If she showed in vivo evidence of poor tolerance, I may have a lower threshold to abort the remainder of her pelvic RT given the need for MTX to control her AI processes.