After residencies in internal medicine and clinical oncology he moved to the Massachusetts General Hospital in Boston, USA for a fellowship in radiation biology. Since joining the staff he has authored over 100 original articles and reviews on many aspects of GU cancer. His particular research interests are in the specific roles of active surveillance, brachytherapy, hormone therapy, and proton beam therapy in the treatment of prostate cancer. He also has a long-standing interest in the organ-sparing management of bladder cancer. He is currently the Jenot and William Shipley Professor of Radiation Oncology at Harvard Medical School, President of the American Society for Radiation Oncology (ASTRO), and a trustee of the American Board of Radiology.