More dramatic, unexpected evidence of selenium’s cancer-preventive properties comes from a 2006 study. Seeking to determine the maximum tolerable dose of the anti-cancer drug irinotecan, researchers administered a massive dose of selenomethionine (containing 2200 mcg of selenium) to protect against the drug’s toxicity. 59 Selenium supplementation was begun one week before the first dose of irinotecan was administered to colon cancer patients who had previously not responded to chemotherapy. This small study of highly drug-resistant patients produced unexpected responses (one patient out of six showed a partial response to treatment) and disease stabilization. No adverse effects of the high dose were reported. The scientists recommended further study of high-dose selenomethionine to determine the most protective serum concentrations of selenium.