Madrid, Spain: THC administration decreases recurrent glioblastoma multiforme (GBM) tumor growth in humans, according to the findings of the first-ever clinical trial assessing cannabinoids' anti-tumor action.

Investigators at Complutense University in Spain administered THC intratumorally in nine patients diagnosed with recurrent GBM, an extremely rapid and lethal form of brain tumor. Patients in the study had previously failed standard therapy (surgery and radiotherapy) and had clear evidence of tumor progression. THC treatment was associated with reduced tumor cell proliferation in two subjects, authors reported.

Investigators did not determine whether THC positively impacted patients' survival, though they did conclude that cannabinoid therapy does not facilitate cancer growth or decrease patients' life expectancy. Median survival of the cohort from the beginning of cannabinoid administration was 24 weeks, and two patients survived for approximately one year. Survival for GBM patients following diagnosis is typically six to twelve months.

Researchers speculated that newly diagnosed glioma patients may respond more favorably to cannabinoid-based therapies.

Investigators also reported that THC demonstrated significant anti-proliferative activity on human GBM cells in culture.

"The fair safety profile of THC, together with its possible anti-proliferative action on tumor cells reported here and in other studies, may set the basis for future trials aimed at evaluating the potential antitumoral activity of cannabinoids," investigators concluded.

In 2005, investigators at the California Pacific Medical Center Research Institute in San Francisco reported that THC selectively decreases the proliferation of malignant cells and induces cell death in human GBM cell lines. Healthy cells in the study were unaffected by THC administration.

Separate preclinical studies indicate that cannabinoids and endocannabinoids can stave off tumor progression and trigger cell death in other cancer cell lines, including breast carcinoma, prostate carcinoma, colectoral carcinoma, skin carcinoma, and pancreatic adenocarcinoma.

Full text of the study, "A pilot clinical study of delta-9-tetrahydrocannabinol in patients with recurrent glioblastoma multiforme," appears in the July issue of the British Journal of Cancer. Abstracts of the study are available online at: http://www.nature.com/bjc/journal/v95/n2/abs/6603236a.html. Additional information on cannabinoids' anti-cancer properties is available in NORML's report, "Cannabinoids as Cancer Hope," online at: http://www.norml.org/index.cfm?Group_ID=6814