There are no issues here as far as radiation requiring a mother to stop
breastfeeding.  No references necessary either.  How would radiation affect
the milk?  It won't and any radiation oncologist who knows his business
would know that too.

However, there is an issue.  If she gets radiation to the chest, the
radiation may adversely affect the milk producing cells and actually kill
them.  The mother should make sure that as much as is reasonable while still
treating her disease, the breasts be protected from radiation.  (not because
of adverse effects on the milk and the baby).

Jack Newman, MD, FRCPC