Verified answer

Radiotherapy is a local treatment, and only causes hair loss if it is directed to a part of the body that is hairy, such as the head.

I suspect you're confusing radiotherapy with chemotherapy. Many, though not all, chemotherapy drugs cause hair loss; and that hair loss can include facial hair and eyebrows

Radiotherapy causes hair loss just like chemotherapy. However, with radiation it is a localized hair loss. I had radiation from my head to my tail bone and lost all my hair, eyebrows, and eyelashes. It also depends on the degree of radiation. Your radiologist is the best person to talk to about hair loss and other side effects. I wish you luck.

Hope this helps :))