Not to be short, but..If your doctor is prescribing it, YES. It isn't as bad maybe as what you could be thinking. In some cases radiation is all you can have, no chemo, so you definitely need it.
I've been through radiation twice, two different cancers, and chemo twice for one cancer. If my dr. told me today I had to have it, I'd say when and where. It beats the alternative.
If you have any questions about how it affects you, feels, etc. please ask, lot's of us have had it, LOTS of times.
Hope your doing well!