Low-income cancer patients are much less likely to participate in clinical trials than their more affluent peers, a U.S. study confirms.

Even after accounting for gender, age, race, travel distance from treatment sites and certain diagnosis details, patients with household income of less than $50,000 a year were 32 percent less likely to enroll in trials than those who make more annually, according to the study published Thursday in JAMA Oncology.

The disparity was even more stark for patients with household income below $20,000, who were 75 percent less likely to join cancer studies than the wealthier people in the study.

"Low-income patients are likely more sensitive about how to pay for clinical trial treatment, including direct costs like co-pays and co-insurance, or indirect or hidden costs such as taking time off work for extra clinic visits," said lead study author Joseph Unger, a biostatistician at the Fred Hutchinson Cancer Research Center in Seattle.

While some previous survey research has suggested household finances might be an important predictor of access to clinical trials, the current study confirms this is happening based on patient-level income data collected before participants decided whether to join cancer trials.

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For the current study, researchers analyzed data on 1,262 adults at eight cancer clinics across the U.S. who were diagnosed with breast, lung or colorectal tumors.

Patients joined the study before they made treatment decisions, and were followed for up to six months to see whether or not they opted to participate in a clinical trial.

Most of the participants were women, had at least some college education, lived at least 13 miles away from the treatment center and were younger than 65 years old.

Four out of five participants were being diagnosed with cancer for the first time, and the majority had breast tumors.

Roughly half of them had household incomes of at least $50,000, while another 30 percent had annual incomes of $20,000 to $49,999. About one in five came from households with less than $20,000 a year in income.

One problem with fewer low-income patients joining trials is that this may mean these people are less likely to have access to the newest treatments, including experimental therapies, Unger said by email.

"Patients should have equal access to treatments regardless of their income level," Unger said.

From a research perspective, lower enrollment among low-income patients might slow down the process of starting trials and make it difficult to be certain the results are meaningful for rich and poor alike, he noted.

While there may be ethical concerns about paying patients to participate in trials, it might make sense in some circumstances to consider waiving any out-of-pocket medical costs not covered by insurance to lessen the financial barriers to participation, Unger added.

SOURCE: http://bit.ly/1jEfWWG JAMA Oncology, online October 15, 2015.