[Don Corlemahomes]

The first thing that jumped out at me is that one of these papers has nothing to do with cancer, specifically this study that suggested that cannabinoids could protect the brain against neurodegeneration in neonatal rats caused by the toxin ouabain (an Na+/K+-ATPase inhibitor). The vast majority of the other studies were in human cell lines, such as this one studying the effect of cannabidiol, a nonpsychoactive cannabinoid, on glioma cell lines. As a cancer researcher, I noted that the IC50 (the concentration that produces 50% of maximal inhibition of the parameter being measured), was 25 μM, which is a bit higher than we like for an anticancer compound. I was thus not particularly impressed, although in fairness subcutaneous injection of CBD was able to inhibit the growth of glioma xenografts implanted subcutaneously in athymic nude mice, although no dose-response was demonstrated, and a dose of 0.5 mg per mouse is a pretty generous dose (25 mg/kg for a typical 20 g mouse). So while there does appear to be antitumor effect against the glioma cell lines tested, it was, at best, modest. Certainly it wasn’t the sort that would knock my socks off as a cancer researcher. A different study, which combined THC and temozolomide, produced more impressive results, not for the THC, which produced at best modest antitumor effect, but for the combination, which looked a bit more promising. Of course, one also must note that this is not hash oil or smoked pot, but the purified THC component. That THC might be useful against glioma does not tell us that hemp oil or smoking the weed will be useful against glioma any more than the fact that digoxin works in congestive heart failure tells us that it would be a good idea to ingest foxglove leaves.

Skeptical Raptor puts it in perspective:

In one study, the researchers determined that it would take a concentration of cannabinoids of approximately 10 µmol/L to cause the death breast cancer cells in cell culture. This converts to around 3.14mg/L of THC. So, you’d have to assume that to kill any breast cancer cells, you’d need at least a blood level of 3.14 mg/L to achieve breast cancer cell death. So how close to that 3.14 mg/L can we get by just smoking a joint or two? According to research, smoking one joint will give you a blood level of THC of around 1.3-6.4 ng/mL serum, or about .00013-.00064 mg/L. In other words, to get an anti-cancer effect, you need to light up around 1000 joints per day.

The IC50 values in these studies were higher than 10 μM.

Finally, there was one human study in the list of glioma papers. Basically, this was a phase I trial testing a method of administering THC. This was also some strange science in that nine patients with recurrent glioma had their tumors resected, but a catheter was left in the cavity left behind after surgery, and then:

Each day an aliquot of the THC solution (100 mg ml−1 in ethanol) was dissolved in 30 ml of physiological saline solution supplemented with 0.5% (w v−1) human serum albumin, and the resulting solution was filtered and transferred to an opaque syringe. This process was performed at the Department of Pharmacy of the Hospital Universitario de Canarias. Owing to the high hydrophobicity of THC, we controlled by gas chromatography/mass spectrometry (see below) the actual concentration of THC in the final solution. The THC solution was administered to the patients for different times starting at days 3–6 after surgery at a rate of 0.3 ml min−1 with a syringe pump connected to the subcutaneous reservoir. In the case of Patients 1 and 2, who received THC for 30 and 26 days, respectively, biopsies were also taken after the THC-treatment period and various tumour-cell parameters were evaluated.

As you can see, this is very different from smoking marijuana or ingesting hash oil. It involves directly infusing THC solution at a high concentration directly into the brain cavity where the tumor had been, in the hope of killing off any remaining tumor cells surrounding the cavity. Let’s just put it this way. There’s a reason why direct intratumoral injection of any drug is generally frowned upon, and that’s because it’s invasive and rarely works. Moreover, no one generally bothers with intratumoral infusion of a drug unless it requires a very high concentration to work. Mean survival was 24 weeks, and two patients survived approximately a year. The authors try (rather like Stanislaw Burzynski, actually) to argue that this is better than would be expected based on other studies and controls, and to claim that some patients responded. I find no convincing evidence of this in the paper, and in a cohort of nine patients though, it’s pretty darned hard to conclude this. I agree with Harriet. There is nothing “earth shattering” about these results. They could be consistent with an antitumor effect, but they could just as easily be consistent with no effect. Worse, this was not simply ingesting, smoking, or being injected with cannabinoids. The study involved having catheters sticking out of the subjects’s heads and having THC infused directly into the brain.

https://www.sciencebasedmedicine.org...t-cure-cancer/

Just an FYI. The studies just don't support the idea that recreational use of cannabis can shrink tumors. I specifically posted the glioma section of this well-written article because I'm assuming "GBM" is glioblastoma multiforme, which is a malignant growth of glial cells.

In essence, most studies have been done in animal models, and have shown anti-tumor effects at ridiculously high doses (~1000 joints).

I just want to make you aware of what is known and make an educated decision.