Doctors are reporting improved survival in men with advanced prostate cancer from an experimental drug that delivers radiation directly to tumor cells. It’s an approach that could someday treat other hard-to-reach cancers. The study tested an emerging class of medicine called radiopharmaceuticals. The drug in this case is given by IV. It contains two parts: a tracker and a cancer-killing payload. The tracker hunts down cancer cells. The payload emits radiation. Results were released Thursday by the American Society of Clinical Oncology ahead of its annual meeting. The study was funded by the drug company, Novartis.