The Society of Gynecologic Oncology sent out a nationwide survey in recent weeks. In response, doctors in 35 states said they had little to no supply of key chemotherapy drugs, even at large cancer centers and teaching hospitals.

Dr. Patrick Timmins, a partner of Women’s Cancer Care Associates in Albany, N.Y., said his practice ran out of some chemotherapy drugs on May 9, but still has 25 patients who need them.

“Our patients are in a war, and what we’re doing is we’re taking their weapons away,” Dr. Timmins said. “It’s completely ridiculous that we can’t figure out a way, at least in the short run, to get our patients treated, and in the long run to solve these recurring problems.”

When Ms. Bray met with White House staff members in late April, she said that she recommended creating an exchange, to get drugs where they were needed most, and increasing the production of small-batch medicines, often referred to as compounding.

Dr. Kevin Schulman, a professor at Stanford Medicine who has studied the generic drug industry, said he had urged the White House team to examine how much power the intermediary companies have in contracting with generic drug makers. He said they demand rock-bottom prices, but unlike a customer-facing company like Apple that contracts with suppliers worldwide, the drug intermediaries face no accountability when shortages arise.