Many cancer patients are not taking prescribed oral treatments because of high costs, a study led by University of Pennsylvania researchers suggests.

Using a national database of Medicare and private health insurance claims in 2014-15, the researchers looked at whether patients’ unreimbursed expenses were a deterrent to filling prescriptions for 38 therapies given in pill form. Oral drugs are generally newer, molecularly targeted treatments and are more expensive than intravenous cancer drugs.

Overall, 18 percent of the 38,000 patients didn’t fill an oral drug prescription after it was approved by their insurance. But cost was a big factor: Nearly half of those who were charged more than $2,000, and almost a third who owed $100 to $500, skipped their prescribed drug. In contrast, only 10 percent who were charged less than $10 did so.

The patients facing out-of-pocket costs over $2,000 – who made up 12 percent of the group – were also more likely to delay the start of oral therapies, and less likely to switch to an alternative pill or intravenous medication, according to the analysis published online last week in the Journal of Clinical Oncology.

While the problem is clear, the solutions are not, especially as employers continue to shift health insurance costs to workers.

In recent years, 43 states have passed “chemotherapy parity” laws intended to make oral drugs more affordable. Federal legislation is pending. The statutes – which apply only to fully insured health plans, not Medicare or self-funded private plans – require that oral drugs be covered under “no less favorable” terms than intravenous chemotherapies.