I have performed Botox injections on patients who have a history of breast cancer with their oncologist's approval. Some patients might have a weaker immune system or their blood counts might be affected, but provided that there is not a high probability of bruising nor higher risk of infection with their current immune status, then Botox is done and works on them just as well as my patients who aren't undergoing chemotherapy or radiation therapy.I think it helps those with such conditions to feel that doctors are not giving up on them and it is perfectly appropriate and normal for a patient with breast cancer to desire improvement in their appearance. It can help them feel better about themselves which can have a direct effect on improving their immune system and may help them cope emotionally and physically better with their breast cancer.The information provided in Dr. Shelton's answer is for educational purposes only and is not intended to constitute medical advice. The information provided should not be relied upon as a substitute for consultations with a qualified health professional who may be familiar with your individual medical needs.