Such drug shortages could affect people with colon cancer, breast cancer and leukemia. They include chemotherapy drugs prescribed after a tumor has spread.
"These are drugs used for common and curable cancers," Dr. Keerthi Gogineni of the Hospital of the University of Pennsylvania in Philadelphia told Reuters Health.
"It is becoming increasingly difficult for patients with cancer to receive the lifesaving treatments they need," she and her colleagues write in a letter published in the New England Journal of Medicine. The shortages "compromise the delivery of standard cancer care and lead to higher costs."
Their work builds on an earlier survey, released in March, of pharmacists and other health professionals who buy cancer drugs for hospitals. In that study, 16 percent said shortages had caused problems for patients, including more disease progression or additional treatment-related complications.
A co-author of that survey, James M. Hoffman, said the new study "adds additional evidence for the harmful consequences of chemotherapy drug shortages on cancer patients."
Hoffman is the medication outcomes and safety officer at St. Jude Children's Research Hospital in Memphis, Tennessee.
"It demonstrates that chemotherapy shortages frequently force chemotherapy regimens to be changed or delayed, which may lead to increased costs or even worse outcomes," he told Reuters Health in an email.
One report published a year ago found fewer patients survived Hodgkin lymphoma - a type of immune system cancer - when doctors had to switch from using the standard chemotherapy drug to a substitute.
Such shortages have happened in the U.S. since 2006 but have been becoming more common. In October, the U.S. Food and Drug Administration (FDA) issued a strategic plan designed to prevent shortages and proposed requiring drug companies to promptly notify it if a supply problem looms. But the FDA cannot compel action to prevent a shortage.
"In the last five years, there's been a three-fold increase in the number of shortages reported," Gogineni said.
Sometimes shortages happen because a company didn't make enough of a given drug. Or the company could be trying to get more people to use a more profitable drug instead of a less profitable one.
To gauge the current problem, Gogineni's team sent surveys to 454 cancer doctors in late 2012 and early 2013; 250 responded.
The vast majority - about 83 percent - said they couldn't prescribe the preferred drug at least once in the last six months.
More than three-quarters of them said the shortages forced major changes in treatment. That included switching to different drug combinations, delaying treatment or skipping doses.
Most doctors who encountered shortages said they had to substitute more expensive brand-name drugs for cheaper generic versions. For instance, some reported using a colon cancer drug that is 140 times more expensive per cycle than the drug that was unavailable, Gogineni and her colleagues wrote.
"One thing we were surprised about was that, despite the frequency of shortages, nearly two-thirds of the oncologists we surveyed had no formal guidance to try to make the right next-best decision" when seeking a substitute drug, Gogineni said.
"There ideally should be guidelines to help physicians manage shortages so they know there's a specific alternative drug."
The survey couldn't determine how many patients are likely to be affected by drug shortages. Gogineni said people with cancer should ask their doctor whether they might be affected.
"Knowing at the outset that there might be a change or modification of the treatment plan is something patients should be advised of as soon as possible rather than be surprised by it," she said. It may allow them to go somewhere else, where the supply is sufficient, to complete their treatment.
William Greene, St. Jude's chief pharmaceutical officer, said the survey shows the problem is particularly severe for patients treated in private or community settings.
"Much of the previous discussion on shortages has come from large health-systems and academic settings," he told Reuters Health in an email. "Smaller office-based practices often do not have the market power or other resources to obtain needed drugs in a shortage situation."
SOURCE: http://bit.ly/1cAW8sg New England Journal of Medicine, online December 18, 2013.