Vitexina, a product containing the flavonoid vitexin as the main component, is derived from a plant, Vigna radiata (L.), that has been traditionally used in Vietnam for detoxification. This remedy is also used to treat the symptoms of conditions classified as "hot" in traditional medicine. The present study is a randomized, placebo-controlled comparative clinical trial for investigating the radioprotective effects of Vitexina for breast cancer patients undergoing radiotherapy with cobalt-60. No relevant weight loss, (even weight gain), occurred in 70% of patients in the Vitexina group, whereas 73% of the placebo group lost 1 to 2 kg of weight after 6 weeks of radiation therapy. The administration of Vitexina produced a significantly protective effect in peripheral blood cells in amount and in lymphocyte blast-transformation function. Condition of hot was observed in almost all cancer patients in this study by tongue examination. Hot condition did not change in the Vitexina group, but the incidence of hot and extreme hot cases were significantly increased in the placebo group after 6 weeks of radiation therapy. The results suggest that application of medicinal plants of the "clearing heat and detoxification" classification as an adjuvant would be a potential solution in integrative cancer therapy.