Cannabis use was associated with shorter time to progression (TTP) and overall survival (OS) among patients with advanced cancer receiving treatment with immune checkpoint inhibitors (ICIs), according to an observational study reported at the European Society of Medical Oncology (ESMO) Virtual Congress 2020.

“Cannabis or cannabis derivatives are widely used by patients with cancer to help with cancer symptoms and treatment side effects,” Gil Bar-Sela, MD, of the Emek Medical Center in Israel, and lead author of the study, said. “However, cannabis has potent immunomodulatory properties.”

The single-center, prospective, observational study included 102 consecutive patients with advanced cancers who were planned to receive treatment with ICIs. Of these patients, 34 used cannabis in addition to their ICI. Blood samples were collected prior to initiation of ICI treatment. Endocannabinoid (eCB) blood levels were evaluated in 36 patients. The primary post hoc endpoint was TTP and OS, and the secondary endpoint was eCB concentrations.

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Cannabis use was associated with significantly shorter TTP with a median of 3.4 months compared with 13.1 months among patients who did not use cannabis (P =.0025). OS was also shorter with cannabis use, with a median of 6.4 months compared with 28.5 months with no cannabis use (P =.0009).

ICI treatment, but not use of cannabis, was associated with changes in endogenous eCB levels. Endogenous eCB levels appeared to be associated with OS, “suggesting that the effect of eCB and eCB-like lipids on immunotherapy success rates should be further examined,” Dr Bar-Sela said.

Dr Bar-Sela concluded that “we provide here the first indication of the effect of cannabis consumption during ICI immunotherapy treatment and show it may be associated with worsening clinical outcomes when compared to non-users.”


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.