I remember when a woman I know (we'll call her P) was receiving radiation after a radical mastectomy, her biggest complaint was the skin symptoms she endured during treatment.
P constantly talked about her skin "weeping" and the frustration of not being able to wear deodorant. The pain and peeling skin were so bad mid-treatment that she didn't leave the house and walked around without a shirt on to avoid anything touching her irradiated skin.
P was told by her oncologist (and she knew from her own mother's experience) that skin damage happens during radiation; however, she did not realize how much it would dominate her life. Like many side effects of radiation (diarrhea, fatigue, hair loss, vomiting), the changes to her skin changed how P lived her life. Everything from how she bathed, slept, and dressed changed during and post treatment.
While we do not want to scare patients, telling them the side effects of radiation therapy are going to be bad, we can impress upon them that it's not a matter of if but when their bodies are going to react to treatment and discuss openly the side effects and ways to manage them when they come.
Resources to guide the conversation
There are several places you can send patients online to get more information.
Your presence and guidance
More important than any pamphlet is your presence and guidance in this area; ask radiation therapy patients how they are doing, but also ask to see their skin. You may be able to see coming skin issues that a patient thinks are "OK" or hasn't really noticed because of other side effects.
Also, talk to patients about how the skin side effects are affecting how they are seeing their therapy and its progress. For P, the worse her skin got, the more she wanted to avoid therapy and feared it. Being able to express those thoughts is important for a patient's commitment to therapy.