Cannabis inhalation is associated with spontaneous brain tumor regression in two subjects, according to a pair of case reports to be published in Child’s Nervous System, the official journal of the International Society for Pediatric Neurosurgery.

Investigators at the British Columbia Children’s Hospital in Vancouver documented the mitigation of residual tumors in two adolescent subjects who regularly inhaled cannabis. Authors determined that both subjects experienced a “clear regression” of their residual brain tumors over a three-year-period.

“Neither patient received any conventional adjuvant treatment” during this time period, investigators wrote. “The tumors regressed over the same period of time that cannabis was consumed via inhalation, raising the possibility that cannabis played a role in tumor regression.”

Researchers concluded, “Further research may be appropriate to elucidate the increasingly recognized effect of cannabis/cannabinoids on gliomas (brain cancers).”

A 2006 pilot study published in the British Journal of Cancer previously reported that the intratumoral administration of the cannabinoid THC was associated with reduced tumor cell proliferation in two of nine human subjects with brain cancer.

Separate preclinical studies assessing the anticancer activity of cannabinoids and endocannabinoids indicate that the substances can inhibit the proliferation of various types of cancerous cells, including breast carcinoma, prostate carcinoma, and lung cancer.

Commenting on the two new case reports, researcher Jahan Marcu — who has previously documented the inhibitory effects of cannabinoids on human glioblastoma cell proliferation and survival — wrote in the blog Freedom Is Green: “Can marijuana contribute to the regression or remission of certain cancers? Given the slow progress of clinical trials for whole plant Cannabis, it can be frustrating waiting for years, even decades, trying to answer these vital questions. But for the two young women with brain cancer in (this) report, a shift to a cannabis lifestyle may have made a difference.”