Loss of appetite is common among cancer patients, either because the cancer itself or its treatment affects the sense of taste and smell, leading to decreased enjoyment of food. This, in turn, can lead to weight loss, anorexia, a worse quality of life and decreased survival; therefore, finding effective ways of helping patients to maintain a good diet and consume enough calories is an important aspect of their treatment.
Researchers in Canada ran a small pilot study from May 2006 to December 2008 in 21 adult patients with any advanced cancer (except brain cancer) who had been eating less as a result of their illness for two weeks or more. All were either being treated with chemotherapy or had been in the past. The patients were randomly assigned to receive medication from a pharmacist in a double-blind manner, which meant that neither the patients nor the doctors knew which treatment they were receiving. Eleven patients received oral capsules containing delta-9-tetrahydrocannabinol (THC) - the main psychoactive ingredient in cannabis - and eight patients were assigned to the control group to receive placebo capsules. The active capsules contained 2.5mg of THC and the patients took them once a day for the first three days, twice a day thereafter, and they had the option to increase their dose up to a maximum of 20mg a day if they wished; however, most followed the dosing protocol, with three patients in both groups increasing their dose to three times a day. The treatment ran for 18 days.
From patient answers to questionnaires conducted before, during and at the end of the trial, the researchers found that the majority (73%) of THC-treated patients reported an increased overall appreciation of food compared with patients receiving placebo (30%) and more often stated that study medication "made food taste better" (55%) compared with placebo (10%).
The majority of THC-treated patients (64%) had increased appetite, three patients (27%) showed no change, and one patient's data was incomplete. No THC-treated patients showed a decrease in appetite. By contrast, the majority of patients receiving placebo had either decreased appetite (50%) or showed no change (20%).
Although there was no difference in the total number of calories consumed by both groups, the THC-treated patients tended to increase the proportion of protein that they ate, and 55% reported that savory foods tasted better, whereas no patients in the placebo group reported an increased liking for these foods. (Cancer patients often find that meat smells and tastes unpleasant and, therefore, they eat less of it).
In addition, THC-treated patients reported better quality of sleep and relaxation than in the placebo group.
Dr Wendy Wismer (PhD), associate professor at the University of Alberta (Edmonton, Canada), who led the study, said: "This is the first randomized controlled trial to show that THC makes food taste better and improves appetites for patients with advanced cancer, as well as helping them to sleep and to relax better. Our findings are important, as there is no accepted treatment for chemo-sensory alterations experienced by cancer patients. We are excited about the possibilities that THC could be used to improve patients' enjoyment of food.
"Decreased appetite and chemo-sensory alterations can be caused by both cancer and its treatment; untreated tumors cause loss of appetite, and by itself, chemotherapy also causes loss of appetite. In any individual patient, some part of both of these effects is usually present.
"It's very important to address these problems as both appetite loss and alterations to taste and smell lead to involuntary weight loss and reduce an individual's ability to tolerate treatment and to stay healthy in general. Additionally, the social enjoyment of eating is greatly reduced and quality of life is affected. For a long time everyone has thought that nothing could be done about this. Indeed, cancer patients are often told to 'cope' with chemo-sensory problems by eating bland, cold and odour-less food. This may well have the result of reducing food intake and food enjoyment."
The researchers say that larger, phase II trials should test their findings further, but, in the meantime Dr Wismer thinks that doctors could consider THC treatment for cancer patients. "It could be investigated for any stage of cancer where taste and smell dysfunction and appetite loss has been indicated by the patient," she said. In addition, treatment would not necessarily have to be limited to the 18 days of the study. "Long term therapy with cannabinoids is possible, however, in each case this would be up to the patient's physician to determine."
Although the study was unable to show that THC treatment could increase total calorie intake, Dr Wismer said this was unsurprising. "In the healthy adult population, we know from personal experience that we usually eat more of something if it tastes better. However, in this advanced cancer population, there is a real struggle with appetite; normal appetitive pathways do not seem to be functioning. We know from our earlier work that individuals with advanced cancer have diminished appetite and have to make a big conscious effort to eat; they are motivated to eat simply to survive. So, although THC did not significantly increase total calorie intake, the fact that it improved appetite and protein intake is important."