Women taking breast cancer drugs are more likely to skip days or drop the treatment entirely if their co-pay is high, U.S. researchers have found.

It's nothing new that people often don't take the medication their doctor prescribes, but for cancer drugs the consequences could be dire, experts say.

"Here we are talking about a life-saving drug," said Dr. Alfred Neugut of Columbia University Medical Center in New York, whose findings appear in the Journal of Clinical Oncology.

"For drugs that are that important, maybe we need to set up mechanisms to provide ways to get around the co-pays or deductibles."

Some insurance companies already have programs in place to ensure lower co-pays for certain drugs, Neugut said, but they don't cover aromatase inhibitors, the focus of the new study.

Such drugs, including AstraZeneca's Arimidex, significantly lower the risk of death in breast cancer survivors who've gone through menopause.

While Arimidex can now be bought as a generic drug for only less than a dollar per pill, the drug cost more than $2,000 a year when the study was done.

Neugut and his colleagues used claims data from MedCo Health Solutions to find out what role patient co-pay might play in whether or not they took their drugs for the recommended five years.
Of more than 8,000 women aged 50 to 65, 20 percent stopped the medication early if their co-pay was less than $30.

By contrast, if the co-pay was $90 or more, 23 percent dropped the drugs ahead of time.
For older women, the gap was five nearly percent, which Neugut chalks up to less disposable income.

There were similar differences in the number of women who skipped at least 20 percent of days, and the gap remained even after the researchers considered possible explanations such as income and other factors.

"If the co-pay gets too high, it is going to stop people from taking a drug they really need," said Neugut, adding that earlier research has noted the same effect for prescriptions as a whole.

With the healthcare reform, more people are expected to be covered by Medicaid, which generally means they will have lower co-pay. Yet Neugut said it's unclear what effect that will have, given Medicaid beneficiaries have fewer resources to begin with.

He said the problem was more serious for cancer drugs than for other medicines, because the former treat a potential deadly disease.

In addition, cancer drugs have side effects, which may also deter women from taking them.

In general, Neugut told Reuters Health, "Less than 50 percent of women actually finish the five years—and if you don't, you lose most or all of the survival benefit from the therapy."