Dear editor:

We have read with interest the article by Lobos Urbina and Peña Durán (Medwave 2016;16(Suppl3):e6539 doi: 10.5867/medwave.2016.6539) [1]. Cancer pain is a complex symptom, its control is influenced by many factors: the pain mechanism (neuropathic versus non neuropathic), pain characteristics (continuous versus incidental), previous opioid dose, cognitive function, psychological distress, tolerance and past history of alcohol or drugs [2].The majority of the studies cited by Lobos Urbina and Peña Durán did not control these variables.

Pre-clinical data suggest the utility of cannabinoids for treating pain [3]. Clinical evidence has reported that cannabinoids are useful drugs for treating chronic pain, neuropathic pain, and that refractory to the standard treatments [4]. In systematic reviews and meta-analysis, patients with cancer pain have been heterogeneously represented in comparison with pain due to other conditions. The most encouraging result has been reported in the treatment of post chemotherapy neuropathic pain and irruptive pain [5],[6].

Secondary effects have been the most frequent argument in view to avoid the use of cannabinoids in the treatment of cancer pain, although other drugs used with the same goal also have important risks. Therefore, judgement on relative risk/benefits should be considered within the broader context of risk/benefit of other agents as well.

Nowadays cannabinoids cannot be considered as a standard treatment in cancer pain neither for all types of pain due to cancer. There are other drugs and treatments with proved effectiveness that remain as the first treatment options. However, nearly 20% of patients will develop a refractory pain in spite of an optimal treatment.

Lobos Urbina and Peña Durán express that any analgesic effect of cannabinoids would be small and, due to its risk/benefit balance, patients and physicians should be against its use. We think this is a ventured asseveration because the authors recognize the high probability that the results of their meta-analysis may change in the future. If there is evidence suggesting a specific role of cannabinoids, why physicians should be against that? Why should we give up exploring its role in cancer patients without other treatment options? Why not study cannabinoids in cooperative and well-designed studies?

We appreciate that the study of Lobos Urbina and Peña Durán addresses this issue because of the connotation of medical use of cannabis in the public opinion and the recent authorization by the Instituto de Salud Pública to commercialize Sativex ® in Chile.