Cancer therapy with phytochemicals: evidence from clinical studies

Cancer is still one of the major causes of mortality in both developing and developed countries. At present, in spite of intensive interventions, a large number of patients suffer from poor prognosis. Therefore, the effort for finding new anticancer agents with better efficacy and lesser side effects has been continued. According to the traditional recommendations and experimental studies, numerous medicinal plants have been reported to have anticancer effect. Also antiproliferative, pro-apoptotic, anti-metastatic and anti-angiogenic effects of several phytochemicals have been shown in in vitro experiments or animal studies. However, only a small number have been tested in cancerous patients and limited evidence exists for their clinical effectiveness. Also, regarding some phytochemicals, only beneficial effects on cancer-related symptoms or on quality of life have been reported and no positive results exist for their antitumor actions. This review was focused on the phytochemicals whole beneficial effects on various types of cancer have been supported by clinical trials. Based on the literature review, curcumin, green tea, resveratrol and Viscum album were the satisfactory instances of clinical evidence for supporting their anticancer effects. The main findings of these phytochemicals were also summarized and discussed.