A systematic review assessing 19 studies that evaluated premalignant or malignant lung lesions in persons 18 years or older who inhaled marijuana concluded that observational studies failed to demonstrate statistically significant associations between marijuana inhalation and lung cancer after adjusting for tobacco use.
With a hypothesis that chronic marijuana use produces adverse effects on the human endocrine and reproductive systems, the association between marijuana use and incidence of testicular germ cell tumors (TGCTs) has been examined.[9,10,11] Three population-based case-control studies report an association between marijuana use and elevated risk of TGCTs, especially nonseminoma or mixed-histology tumors.[9,10,11] However, the sample sizes in these studies were inadequate to address marijuana dose by addressing associations with respect to recency, frequency, and duration of use. These early reports of marijuana use and TGCTs establish the need for larger, well-powered, prospective studies, especially studies evaluating the role of endocannabinoid signaling and cannabinoid receptors in TGCTs.
A comprehensive Health Canada monograph on marijuana concluded that while there are many cellular and molecular studies that provide strong evidence that inhaled marijuana is carcinogenic, the epidemiologic evidence of a link between marijuana use and cancer is still inconclusive.
No clinical trials of Cannabis as a treatment for cancer in humans were identified in a PubMed search; however, a single small study of intratumoral injection of delta-9-THC in patients with recurrent glioblastoma multiforme reported potential antitumoral activity.[13,14]
Despite advances in pharmacologic and nonpharmacologic management, nausea and vomiting (N/V) remain distressing side effects for cancer patients and their families. Dronabinol, a synthetically produced delta-9-THC, was approved in the United States in 1986 as an antiemetic to be used in cancer chemotherapy. Nabilone, a synthetic derivative of delta-9-THC, was first approved in Canada in 1982 and is now also available in the United States. Both dronabinol and nabilone have been approved by the U.S. Food and Drug Administration for the treatment of N/V associated with cancer chemotherapy in patients who have failed to respond to conventional antiemetic therapy. Numerous clinical trials and meta-analyses have shown that dronabinol and nabilone are effective in the treatment of N/V induced by chemotherapy.[16,17,18,19] The National Comprehensive Cancer Network Guidelines recommend cannabinoids as breakthrough treatment for chemotherapy-related N/V.