Effective ultra-low doses of erlotinib in patients with EGFR sensitising mutation.

We describe three cases of patients with advanced adenocarcinoma of the lung and epidermal growth factor receptor (EGFR) mutation treated with erlotinib 25 mg/day and 25 mg every second day, being equal to one-sixth and one-twelfth of the recommended dose. The mean age of our patients was above 70 with a WHO performance status 1 before and during the treatment. The reasons for erlotinib dose reduction were rash, diarrhoea and fatigue. The decision was a result of lack of other treatment options and radiological response on standard doses. We did not observe any liver enzyme abnormalities. However, the post-treatment creatinine increased significantly. As of February 2014, our patients are still on treatment with tolerable side effects and improved quality of life. These findings indicate that some patients responding to erlotinib with noxious side effects could have clinical benefit in doses much lower than recommended.