That's a good point about the chemo, Chick. Having had chemo appears to make a great deal of difference to treatments following on, such as endocrine therapy and radiotherapy.
Here's a bit on the Cancer Research UK site about dying hair after chemo.
Using hair dye
It is best not to use dyes or perms for around 6 months after finishing chemotherapy. This is because when you are recovering from chemotherapy, your hair is more fragile than usual. It is more likely to get damaged.
It takes about 6 months for the hair to become stronger. It isn't a good idea to use:
These products contain strong chemicals that can damage your hair. Your scalp may also be drier and itchier than normal during this time. Using strong chemicals on your hair can make this worse.
Henna and vegetable based dyes
It's understandable that you might not want to wait to dye your hair. You can ask your hairdresser to suggest henna dyes or vegetable based dyes for you. These are gentler on the hair than the other types of hair colouring. So hair specialists think it is safe to use them.
Even with a vegetable dye, it is worth testing before you use it. You can test the dye on a small section of your hair first to see how it works.
How chemotherapy might affect your hair
This will depend on which chemotherapy drugs you had. Some types of chemotherapy make hair fall out completely. Other types make the hair thin, or change in texture.
You might find that your hair doesn’t grow back exactly the same as it was before. Here's some possible changes that might happen to your hair:
I can't find anything on Breast Cancer Care, Cancer Research UK or Macmillan to suggest that readiotherapy to the breast affects the hair on you head.
I am in agreement with Appletree.
If you are talking about breast and axilla radiotherapy then this should not affect hair colouring or cutting (unless underarm hair 😁).
I would contact your radiotherapy department and ask for an explanation. If a radiologist is advising this to breast patients then they need some extra training.
Another possibility, have you just finished chemo recently and if so, were they possibly advising on that?
Best wishes to you, 🐣 Chick X
This sounds extraordinary. Did you have any part of your head irradiated?
I was not given any such instructions. It was my left breast and the lower part of the axilla that were treated. My head was right out of the line of fire. I was able to wear earrings throughout the treatment and wash my hair as much as I wanted. The X-ray beams were very precisely targeted.
You could check with your GP, who might be able to contact the radiologist for you and get clarification of this.