Comparing cannabinoid extracts for treating cancer-related symptoms: a randomized placebo-controlled, triple-blind aggregate n-of-1 clinical trial

Context Despite widespread use of medical cannabinoids for cancer-related symptom management, systematic reviews consistently call for more clinical trial evidence. Objectives This study aimed to determine and explore responses to medical cannabis extracts for cancer-related symptoms using patient-centred methodology. Methods An aggregate N-of-1 study of clinically stable but symptomatic outpatients from 8 Canadian cancer centres, comparing three blinded sublingual extracts (THC; CBD; 1:1) with placebo, self-titrated within a prescribed schedule for four consecutive days each in randomized sequence for up to three cycles (total 16-48 days). The primary outcome was the frequency of at least a 1.4-point (20%) improvement in a 7-point Patient Global Impression of Change (PGIC) for at least one extract over placebo. Results The primary outcome was achieved in 50/89 (56%) participants (p<0.001), with no significant preference of one extract over another on average, but a clear preference between extracts for most individuals. Changes in a modified Edmonton Symptom Assessment score and participant preference (n=91) confirmed these findings. Improved sleep, tiredness and anxiety contributed most to the overall improvement regardless of primary symptom. There were no demographic predictors of response. Mild adverse effects were common with all extracts including placebo but resolved rapidly on dose reduction/cessation. Moderate/severe adverse effects were rare but associated with THC. Conclusions Medical cannabis extracts can be meaningfully beneficial for cancer-related symptoms in approximately 50% of patients, particularly for sleep and related symptoms. A starting dose of 2.5mg of THC/CBD three times a day was well-tolerated. Personalization of treatment is required to optimize response.