Hi thanks for asking question. Yes radiotherapy lead to few or more side effect depend upon individual mostly 2 week after starting radiotherapy. Here in your case side effect may be diarrhea, rectal bleeding, incontinence, lower sperm count. Here is some better advise for you to minimize the side effect. Take adequate rest. Eat healthy balanced nutritional diet. Skin over pelvis are should be clean.avoid to apply any irritant cream or moisturizer. Vitamin tablets helpful. Radioprotective drugs are helpful. But still with best preventive measures side effects very. I hope I have solve your query. Avoid stress.