In 3rd week of pelvic radiation therapy. 3 days ago my body started itching, still itching but little to no rash. mostly my arms and legs are itchy. ?

See your doctor: This is a problem that necessitates a face-to-face meeting with your doctor. This will allow him/her to examine you, ask specific questions. And possibly order tests to find out what's wrong and what to do to help you.

Probably not related: Pelvic radiation will cause pelvic symptoms. Itchy arms and legs may well be related to a new medicine you are taking. Symptoms outside the radiated area are unlikely to be caused by radiation.