One of the therapies that has arisen within conventional veterinary medicine, but which shares many of the worrisome features of an alternative approach, is stem cell therapy. Though it is a plausible intervention with promising preclinical evidence to support investigating its possible clinical benefits, it remains an unproven and inadequately investigated form of treatment. As a result, it is currently legal for human use in the U.S. only under very restricted conditions. Unfortunately, many people seek such therapies in other countries with less robust laws and regulations protecting the public, through so-called “medical tourism.” And since the same strong public health laws rarely apply to our veterinary patients, stem cell therapies are aggressively marketed in the U.S. despite having even less evidence to support their use than is available for human medical uses.
I have written about this marketing and about the concern researchers in human stem cell therapies have expressed about the premature clinical use of inadequately tested stem cell treatments. Some of these researchers have recently reiterated their cautions about medical tourism and stem cell therapies, and their arguments are just as applicable to the domestic market in veterinary stem cell treatments.
Master Z, Resnik DB. Stem-cell tourism and scientific responsibility.EMBO Rep. 2011 Jul 29.
With a few exceptions—such as the use of bone-marrow haematopoietic cells to treat leukaemia—novel stem-cell therapies are often unproven in clinical trials. Even well-proven therapies can lead to tumour formation, tissue rejection, autoimmunity, permanent disability and death. The risks of unproven and unregulated therapies are potentially much worse…
Any medical innovation is ethically responsible when it is based on animal studies or other research that guarantee evidence of safety and clinical efficacy. Adequate measures must also be taken to protect patients from harm, such as clinical monitoring, follow-up, exclusion of individuals who are likely to be harmed or are unlikely to benefit, use of only clinical-grade stem cells, careful attention to dosing strategies and informed consent.
The authors also address the issue of educating patients and doctors about the inadequate evidence for most stem cell therapies and the dangers of employing these therapies without a clear understanding of their risks and benefits. Their conclusions, however, are disappointing for those of us involved in such educational efforts, regarding both stem cell therapy and other kinds of unproven or even disproven methods.
Educating patients about the risks of unproven therapies can also help to address the problem of stem-cell tourism. However, education too has significant limitations, since many people will remain ignorant of the dangers of unproven therapies, or they will simply ignore warnings and prudent advice. For many years, cancer patients have travelled to foreign countries to receive unconventional and unproven treatments, despite educational campaigns and media reports discussing the dangers of these therapies. Since the 1970s, thousands of patients have travelled to cancer clinics in Mexico to receive medical treatments not available in the USA.
Education for physicians on the dangers of unproven stem-cell therapies can be helpful, but this strategy also has limitations, since many will not receive this education or will choose to ignore it. Additionally, responsible physicians might still find it difficult to persuade their patients not to receive an unproven therapy, especially when conventional treatments have failed. The history of cancer treatment offers important lessons here, since many oncologists have tried, unsuccessfully, to convince their patients not travel to foreign countries to receive questionable treatments.
Given the lack of impact educational efforts often have on patient and clinician behavior, another possible method for limiting the potential harm of inadequately tested therapies is regulatory oversight requiring a reasonable degree of scientific evidence before such therapies can be marketed outside of the clinical research and compassionate use contexts. This has worked to prevent much inappropriate use of stem cell therapies in humans in the U.S., though the practice of medical tourism is a way around such regulations. Regulations on veterinary therapies are far less restrictive, and this has both benefits and costs. Lax regulation makes investigating novel therapies easier and cheaper, which may lead to more rapid and affordable development of new therapies. However, the same loose regulatory environment also subjects pets and their owners to unproven therapies which may not benefit them and may even be harmful. In any case, regulation is often not an especially effective way of constraining the use of therapies not supported by reasonable scientific evidence.
The recommendation these authors make for reducing stem cell tourism involves denying essential materials to practitioners overseas who use unproven stem cell therapies. This is, obviously, not relevant to the issue of veterinary stem cell therapies marketed in the U.S. What is relevant is the fact that leading researchers into stem cell therapies for humans, those scientists most likely to believe in the promise of such therapies because they have made investigating them their life’s work, are consistent in warning against the premature clinical use of these treatments without adequate supporting research evidence. Caution about such therapies seems prudent when even their advocates recommend it.