A drug used to extend the lives of people with advanced prostate cancer is in short supply and will be for months, leaving some patients with no treatment option as the manufacturer works to ramp up production. The Food and Drug Administration said last week the availability of Pluvicto is limited as manufacturer Novartis AG struggles to meet demand. The drug maker said the shortage stems from manufacturing and delivery issues. Novartis said it is prioritizing the supply for patients who have already started the six-course regimen as it manages the shortage. Novartis is also “taking the difficult but necessary step” of halting the addition of new patients for the treatment as they try to increase supply, said spokeswoman Julie Masow. Pluvicto was approved by the FDA last year for use in patients with a specific type of metastatic prostate cancer, in which the cancer has spread to other parts of the body and the patient has undergone other treatments. It is the only treatment of its kind available. In a pivotal study, subjects who received the drug lived a median of around 15 months, four months longer than the median for patients without it, according to Novartis. Patients who are eligible to be treated with Pluvicto have been treated with standard therapies, but their cancer continues to get worse, according to doctors. Without Pluvicto, some may go back to trying the standard therapy, doctors said. That might include different versions of the same treatment, they said, such as an alternative chemotherapy. For patients who have cancer concentrated in their bones, there is an alternative therapy. But many have tried all available standard options, said Delphine Chen, director of molecular imaging and therapy at Fred Hutchinson Cancer Center in Seattle. “If we can’t start them, we don’t have anything else to offer them,” Dr. Chen said.