Has anyone given Botox to an immunotherapy patient or know of a study?

I have gotten Botox in my forehead for nearly 20 years. Since I was 27! I was recently diagnosed with Stage 3A nodular melanoma. I have had 4 treatments of Opdivo so far and no side effects. I have 8 more to go. I asked my oncologist about getting Botox and he said that because he was not aware of any studies on it, that he says do not do it. Are any doctors on here aware of any studies with Botox and immunotherapy treatments? Having cancer is depressing enough, then I look in the mirror and just want to cry.