Radiation therapy has been used for over 100 years, so techniques have been greatly refined and its curative nature well documented for many cancers. As with any medical intervention, and perhaps most decisions in life, we must always weigh the possible benefits against risks associated with a treatment. That discussion should take place during the initial consultation with your radiation oncologist. There will likely be side effects during therapy and some risk of late or permanent side effects that should be discussed.
Fatigue is a very common radiation side effect, no matter what part of the body is radiated. I encourage patients to be as active as possible during treatment to limit this symptom and to feel strong after it is over. Maintaining a diet high enough in calories to avoid weight loss, and high in protein to repair normal tissues, is also important.
To your husband, best wishes for a successful course of therapy!