Interesting. The deep breathing dovetails with new research that exercise is actually beneficial in fighting cancer. Conventional medicine in it's usual wisdom must have figured that exercise, deep breathing and other things that stimulate circulation and metabolism must have increased metastasis.
So their logical (hmmm) solution was fill the body with toxic chemicals and radiation and slow down the circulation so the body really feels the burn (literally).
Yoga has always been recommended for cancer patients (in alternative medicine) but nice to know there's some science behind it.