Efficacy immune therapy in cancer patients possibly impaired by cannabis use

October 2020 General Willem van Altena
Marijuana leaves in the hands of a medical team Medical background. The concept of oil refining to treat diseases. alternative medicine Natural herbs used to treat diseases.

A lot has been said about the use of cannabis in the prevention or treatment of cancer. Whether cannabis can provide a viable treatment for cancer has been a topic of heated debate for many years now. However, there is little doubt that cannabis does have clinical value in treatment of pain and lifting the burden of cancer treatment by restoring appetite and reducing nausea. But during the recent ESMO virtual annual congress a stern word of warning was heard from an Israeli research team. Cannabis seems to counteract the efficacy of immune therapy.

The findings come from a limited size observational study, involving 102 patients in a single centre in Israel. These patients were treated with immune therapy for a varying array of cancers. In this group of patients, 34 regularly used cannabis products in order to manage effects of their disease or treatment. The researchers took a blood sample at baseline, primary outcome of the study was overall survival (OS) and time to progression (TTP). Secondary outcome was the endocannabinoid concentration in the blood (eCB).

Significantly shorter

The researchers noted that the TTP in patients that used cannabis was significantly shorter than in other patients. Their median TTP was 3,4 months, compared to 13,1 months in patients that did not use cannabis. The OS was also much shorter: median 6,4 months compared to 28,5 months.

According to the reseachers, immune therapy seems to alter the eCB count, and this is associated with a better OS. Using cannabis does not have this effect on the eCB levels. Lead researcher dr. Gil Bar-Sela: “These findings suggest that the effect of eCB and eCB-like lipids on the efficacy of immune therapy needs to be examined more. However, our research does indicate that cannabis use may affect immune therapy, and that there is a possible link between cannabid use and a worse clinical outcome compared to patients who do not use cannabis products.


Bar-Sela G, Choen I, Campisi-Pinto S, et al. Chronic cannabis used by patients with advanced cancer during immunotherapy initiation: clinical outcomes and endocannabinoid levels evaluation. Presented at: European Society of Medical Oncology (ESMO) Virtual Congress 2020; September 19-20, 2020. Abstract 1852P.