I just did a Google search: "No THC during immunotherapy". All the Hits on Google were very disappointing for an old Hippie.

Doctors and their patients should be aware that cannabis consumption may negatively impact outcomes in patients receiving immunotherapy. Findings from an observational study from Israel suggested that cannabis could reduce tumor response to therapy in patients undergoing treatment with the immunotherapeutic drug nivolumab (PMID: 30670598). In another study, these same researchers found that the use of cannabis in patients being treated with checkpoint inhibitor immunotherapy drugs led to a shorter time until their tumors progressed (grew in size and/or spread) and a decreased overall survival compared to those patients not using cannabis (PMID: 32872248).