Shortages of medicines for some of the most common cancers have caused nearly half of doctors to delay treatment and forced about a third to choose between patients needing a particular drug.

The findings from a survey of 250 cancer doctors highlight the anxious situation some of their patients have faced during the past year as manufacturing lapses and changes in the generic-drug industry have cut off the supply of key medicines, said Keerthi Gogineni, a cancer doctor at the University of Pennsylvania, who presented the finding in Chicago at the meeting of the American Society of Clinical Oncology.

More than 80 percent of cancer doctors surveyed said they haven’t been able to get needed medications, including potentially life-saving drugs for breast, ovarian and prostate cancers. While the Food and Drug Administration said it is close to resolving the scarcity, cancer doctors said they expect a continuation of the shortages that have forced them to ration treatments or turn to more expensive alternatives.

“Cancer drug shortages continue to be persistent and pervasive and are affecting the treatment of curable malignancies and adding to our health-care costs,” said Gogineni. “Oncologists are being asked to improvise despite the fact that this has been going on since 2006. We know this is a problem that isn’t going away.”

Skipping Doses

The survey asked doctors about their experience with cancer drug shortages between March 2012 and March 2013. Seventy-eight percent of doctors treated patients with a different drug or regimen because of a shortage while 43 percent delayed a patient’s treatment. Shortages caused 29 percent to skip doses and 37 percent had to choose which patient would be treated and which would have to wait.

In some cases, the shortages have also driven up costs, said Gogineni.

For example, when doctors couldn’t get enough of the chemotherapy drug 5-fluorouracil for gastrointestinal cancer patients, 22 percent switched patients to the drug capecitabine, which costs about 140 times more, the study found. The shortage of 5-fluorouracil has been resolved, the FDA said.

Legislation passed last year that requires drugmakers to notify the agency of potential shortages is fixing the problem, according to the agency.

FDA Notification

Last July, President Barack Obama signed the law requiring drugmakers to notify the FDA if they planned to stop making a product, either permanently or temporarily, or anticipated a shortage because of manufacturing issues. The FDA has also boosted resources devoted to addressing shortages and has worked with foreign drugmakers 17 times since 2010 to fill the supply void, said Valerie Jensen, the FDA’s associate director, drug shortages. The FDA has 25 employees working on each medication shortage, she said.

“What we are seeing is that companies are talking to us sooner, if they notice a quality problem they are letting us know and that helps us intervene,” said Jensen in a telephone interview.

A separate survey presented at the meeting found that 59 percent of cancer doctors said they or a colleague had experienced a drug shortage and that 17 percent felt the problem had gotten worse since last fall. The survey, conducted by the American Society of Clinical Oncology of its members in April, included responses from more than 400 cancer doctors about their experience over the previous six months.

Underlying Causes

While the rules signed into law last year helped the FDA resolve some shortages, it doesn’t address the underlying causes, including consolidation in the generic-drug manufacturing industry and lapses in manufacturing quality, Gogineni said.

Fewer generic drugmakers means there are now just a handful of companies that supply most of the world’s generic medicines. When there is a quality problem at one plant and manufacturing needs to be shut down, it can cause a shortage of dozens of treatments. Drugmakers have also stopped making some older drugs, shifting focus instead to newer, more profitable products.

“We aren’t out of the woods yet,” said Jensen. “These products continue to be vulnerable and we are watching very closely and we think the law is working.”

There are currently 133 medicines in short supply, including 10 drugs for cancer, some of which have been in shortage since 2011, according to the FDA’s website. The FDA is close to resolving all of those cancer drug shortages, Jensen said.

Most of the shortages in 2013 have been of intravenous nutritional products made by American Regent Inc., which had to shut down manufacturing because of quality issues, Jensen said.