Radiation or not after surgery for endometrial cancer?

Excellent. My family member was fine with her 4 week radiation schedule until the end of the third week.
All the best to all those currently in treatment.

My inclination is to follow your doctor’s advice. Endometrial cancer can return—even when you are diagnosed at very early stages. I would at least try the radiation therapy if in your position. Much easier to get through this now than to deal with the possibility of a recurrence, as you may not notice the symptoms until much later.
Whatever you decide I wish you well in your recovery and return to good health.

I had three brachytherapy sessions, and there were no side effects. I was diagnosed with aggressive endometrial cancer, and I wanted to do everything to prevent it from recurring. I wish you a good recovery, but do discuss it more with your doctors.

Go for the radiation! Although I don't know much about brachytherapy, I do know that it is better than external beam radiation: less chance of killing off healthy surrounding tissues. Just wondering why you wouldn't be getting chemo as well.
As for diet and healthy lifestyle, while everyone should follow the regime the effects on cancer may be minimal. Cancer is complicated, operating at the DNA level, so I don't imagine that eating cruciferous veggies and other purported cancer-antagonistic foods would be potent enough to mitigate the course of the disease.
Having said that, there are natural foods and supplements (like pectin) that can ameliorate the effects of radiation.
Hope this helps.