Plain language summary
Lung cancer is the second most commonly diagnosed cancer, generally has a poor prognosis and is the leading cause of cancer mortality. PSK is an immune modulating polysaccharide from the mushroom Coriolus versicolor which has been used in Japan in combination with standard cancer therapy for over 30 years. This systematic review looked at the evidence for the use of PSK in lung cancer and included 11 controlled human trials and 17 preclinical studies. 15 of the 17 preclinical studies supported the anticancer effects of PSK, whilst two studies showed no significant effects. No harmful or negative effects were seen in any of the studies. The review explores the mechanisms by which PSK exerts its anticancer effects. 5 of the human trials were non-randomised and suggest an increased survival of lung cancer patients who received PSK alongside chemo- or radiotherapy, although these studies have methodological weaknesses. All 6 randomised human trials showed benefits on at least one of the following study endpoints: parameters of immune function, body weight, performance score, tumour-related symptoms, or survival. No major adverse effects were reported in the studies reviewed above. There are no known contraindications for use during chemotherapy or radiation therapy. The authors conclude that PSK may significantly improve immune function, tumour-related symptoms, and survival in patients with lung cancer, when used as adjunctive therapy alongside or following standard chemotherapy or radiation therapy, or surgery. PSK appears to increase the tolerability of chemotherapy and reduce limiting factors such as bone marrow suppression.
BACKGROUND Polysaccharide K, also known as PSK or Krestin, is derived from the Coriolus versicolor mushroom and is widely used in Japan as an adjuvant immunotherapy for a variety of cancer including lung cancer. Despite reported benefits, there has been no English language synthesis of PSK for lung cancer. To address this knowledge gap, we conducted a systematic review of PSK for the treatment of lung cancer. METHODS We searched PubMed, EMBASE, CINAHL, the Cochrane Library, AltHealth Watch, and the Library of Science and Technology from inception to August 2014 for clinical and preclinical evidence pertaining to the safety and efficacy of PSK or other Coriolus versicolor extracts for lung cancer. RESULTS Thirty-one reports of 28 studies were included for full review and analysis. Six studies were randomized controlled trials, 5 were nonrandomized controlled trials, and 17 were preclinical studies. Nine of the reports were Japanese language publications. Fifteen of 17 preclinical studies supported anticancer effects for PSK through immunomodulation and potentiation of immune surveillance, as well as through direct tumor inhibiting actions in vivo that resulted in reduced tumor growth and antimetastatic effects. Nonrandomized controlled trials showed improvement of various survival measures including median survival and 1-, 2-, and 5-year survival. Randomized controlled trials showed benefits on a range of endpoints, including immune parameters and hematological function, performance status and body weight, tumor-related symptoms such as fatigue and anorexia, as well as survival. Although there were conflicting results for impact on some of the tumor-related symptoms and median survival, overall most randomized controlled trials supported a positive impact for PSK on these endpoints. PSK was safely administered following and in conjunction with standard radiation and chemotherapy. CONCLUSIONS PSK may improve immune function, reduce tumor-associated symptoms, and extend survival in lung cancer patients. Larger, more rigorous randomized controlled trials for PSK in lung cancer patients are warranted.