Hi @mscoyote, welcome to Connect. This same question has come up in the Lung Cancer group in these discussions:
– Pembrolizumab (Keytruda), Cannabis and Cannabinoids https://connect.mayoclinic.org/discussion/nivolumabkeytruda-cannabis-and-cannabinoids/
- Cannabis oil and Immunotherapy https://connect.mayoclinic.org/discussion/cannabis-oil-and-immunotherapy/

From my understanding, CBD oil interferes with immunotherapy. According to a 2017 study, the "use of cannabis in combination with immunotherapy decreased response rate to treatment, without affecting progression-free survival or overall survival." Here's a link to the study and an article about it.
- 1545PD - The effect of cannabis use on tumor response to Nivolumab in patients with advanced malignancies https://oncologypro.esmo.org/Meeting-Resources/ESMO-2017-Congress/The-effect-of-cannabis-use-on-tumor-response-to-Nivolumab-in-patients-with-advanced-malignancies
- Cannabis Reduces Response Rate to Immunotherapy for Cancer https://www.oncologynurseadvisor.com/home/cancer-types/general-oncology/cannabis-reduces-response-rate-to-immunotherapy-for-cancer/

I didn't find a study specifically about bevacizumab (Avastin). Sounds like this would be an important question for your oncologist. Some people find CBD can help with side effects of treatments. But you wouldn't want to use it if it reduces the effectiveness of treatment, would you? Were you thinking of using CBD for the management of side effects?