Earlier this year two US veterinary doctors conducted a study to assess the anti-tumour and survival effects of yunzhi, a mushroom used in traditional Chinese medicine for more than 2,000 years for its apparent immune-boosting properties.
The doctors tested it on a small group of cancerous dogs, and achieved results similar, if not better, than results obtained with standard chemotherapy.
Dorothy Cimino Brown and Jennifer Reetz, both from the Department of Clinical Studies at the University of Pennsylvania, believe their work may provide enough evidence to provoke a potential shift from reliance on cytotoxic [toxic to cells] therapies to a focus on complementary compounds. This implies potential advances for cancer curative therapies in human and animal health.
In the Ming dynasty (1368-1644), the yunzhi mushroom, Coriolus versicolor also known as "turkey tail" for its uncanny resemblance to one, was boiled to release its restorative qi properties. Past studies have already indicated, but not given clear evidence, that polysaccharopeptide (PSP), a bioactive agent produced from the mushroom, inhibits the growth of induced tumours in animals.
PSP has been widely used in clinical trials in Japan, the mainland and Hong Kong as an alternative method to boost immune status. It has also been used to alleviate chemotherapy symptoms in patients with small-cell lung, oesophageal, breast and gastric cancers. But to date, trials have lacked clear evidence of anti-tumour effects in humans.
The UPenn study randomly divided 15 dogs with splenic haemangiosarcoma - an aggressive, invasive cancer that affects the spleen and commonly strikes golden retrievers and German shepherds - into three yunzhi treatment groups: those on 25 milligrams, 50mg or 100mg per kilogram of body weight per day. The two highest dose groups had median survival times longer than the longest median survival time reported in literature to date.
Dogs that received the highest dose had a significantly slower cancer progression and lived longer than those dogs receiving chemotherapeutic protocols.
Brown, the lead researcher and director of UPenn's Veterinary Clinical Investigation Centre, feels that more rigorous scientific investigation is needed to support the many traditional Chinese or complementary alternative medicines (CAM) used with anecdotal success.
"[Dogs and pets] develop many of the same diseases that people do, and study results not only inform the veterinary community about potential new treatments, but also provide proof-of-concept information for moving to efficacy studies in people," she says.
According to Brown, the cost of the yunzhi product used in the study, called I'm-Yunity, is about US$500 for a three-month course. That would be a lower-priced alternative to the burden of cytotoxic therapy. That is, if yunzhi's safety profile is credible.
Dogs develop cancer about twice as frequently as humans, and one out of every three dogs is affected by canine cancer, according to the US National Canine Cancer Foundation. Advances in veterinary medicine, nutrition and pet-owner education may be helping cherished pets live longer, but there is one possible drawback.
"As a consequence, veterinarians are diagnosing more and more cancers in pets," says Dr Lloyd Kenda, Director of the Valley Veterinary Centre in Happy Valley. Kenda sees many middle-aged and elderly dogs in Hong Kong with splenic haemangiosarcoma, a "dog-only disease" which usually requires total surgical removal of the spleen and related tumours.
"Chemotherapy after surgery has shown to increase the median survival rate, but not to significantly increase the 12-month survival rate. It is a nasty cancer, and even with the best treatment, prognosis is very grave," Kenda explains.
Despite this, Kenda believes his ability to treat these patients has improved because techniques, pharmacology and regimens are constantly being updated. He believes that chemotherapy for several types of animal cancers is "viable, humane and successful".
Professor Chun Kwok-wong, from the department of clinical pathology at Chinese University of Hong Kong, believes Cimino's small pilot study requires further evidence in a larger-scale animal study to confirm the anti-cancer activity of PSP.
In 2005, Chun investigated the effect of yunzhi, combined with another herbal compound, on the immune response in post-treatment breast cancer patients. He concluded that the combination could be beneficial for promoting immunological function. Wong believes that studies on the benefits of PSP on tumours are inconclusive, but thinks it can enhance the immune status of cancer patients.
Chun believes PSP is best utilised as an adjuvant therapy: "PSP should be used in combination with chemotherapy and radiotherapy to relieve patient side effects and improve quality of life."
Cimino will soon conduct another study on dogs with haemangiosarcoma - an aggressive, malignant tumour of blood vessel cells - and treated with PSP, and their morbidity and mortality compared to dogs treated with conventional chemotherapy.
"The cost of performing well-designed, long-term clinical trials in people is very high, but if the next definitive canine study corroborates the data we have to date, it could be well worth the investment to do such studies in people," she says.
The University of Pennsylvania canine study was supported in part from a grant by Integrated Chinese Medicine (ICM) Holdings (Hong Kong), makers of I'm-Yunity, a brand of yunzhi. I'm-Yunity is sold and regulated as a health food supplement in the US. It is not available as a supplement in Hong Kong for people, but will be available to the pet population shortly as a food supplement.