evidence: "There's no two ways about it: [Cannabis] has anticancer properties," Wai Liu, a senior research fellow at St George's, University of London, told Live Science. "But the problem is, how do you translate that into the clinic — and that's the difficult question to address." Here's what we know so far about Mary Jane's cancer-fighting powers. [...] In the first trial, conducted in 2006, scientists showed that THC injections directly into the tumors of patients with brain cancer could safely and effectively inhibit their growth. The trial included just nine patients with glioblastoma. So, although these results were encouraging, the sample size of the study was too small to make any firm conclusions about the drug's safety and efficacy.