Despite improvements in cancer diagnosis and treatment, patients who were uninsured or had Medicaid coverage were more likely to suffer worse outcomes, compared with people who have other forms of health insurance, the studies found.
People who were uninsured or relied on Medicaid were diagnosed at a later stage, received sub-optimal treatment and had shorter survival, the findings showed.
In the case of testicular cancer, they were at greater risk of death from their disease than patients with other insurance, the researchers found.
The findings, published online Aug. 8 in the journal Cancer, add to evidence linking poor outcomes and inadequate health insurance.
Dr. Christopher Sweeney, a medical oncologist at the Dana-Farber Cancer Institute in Boston, is an author of the study examining testicular cancer.
He poses this question: "In a perfect world," if everyone were able to access health care equally, regardless of education and socioeconomic status, "would they have the same outcome?"
"The answer is, I think so," Sweeney said. Some cancers have a biologic component, where ethnicity may play a role, he explained. In this case, though, "the only thing that stood out strongly as a predictor of those who did poorly was the insurance status."
Researchers involved in each of the studies used population-based data from the U.S. National Cancer Institute's Surveillance, Epidemiology, and End Results program.
Sweeney and colleagues identified more than 10,000 men diagnosed with testicular cancer between 2007 and 2011.
The investigators found that uninsured men and patients with Medicaid coverage were at higher risk of being diagnosed with stage II or stage III metastatic disease, and of having larger tumors at diagnosis than men with other insurance.
Among those with metastatic disease, uninsured and Medicaid patients were more likely to have more advanced cancer. "What it means is probably the cancer had been percolating and brewing for longer by the time the patient was diagnosed," Sweeney said.
The study found that uninsured and Medicaid patients with early stage disease were less likely to have their lymph nodes removed, a procedure that may cure some patients. Among patients with advanced disease, the uninsured were less likely to have radiation therapy.
The uninsured and Medicaid patients were more likely to die of their disease and also had a higher risk of death from all causes than men with other insurance, the researchers reported.
The other study involved more than 13,600 patients diagnosed between 2007 and 2012 with glioblastoma, the most common type of brain tumor in adults.
Again, uninsured and Medicaid patients were diagnosed with larger tumors.
Medicaid patients were less likely to have surgery to remove tumors, even though it's the baseline treatment for this cancer, the study found. And uninsured and Medicaid patients were less likely to have radiation therapy, according to the report.
Even after adjusting for multiple factors that might influence the results, having Medicaid or being uninsured was linked to shorter survival. Only patients with other insurance showed gains in survival over time, with patients diagnosed in 2012 living longer than those diagnosed in 2007, the researchers said.
"We definitely think health care access due to insurance status is one of the potential reasons for this difference in the prognosis," said Dr. Wuyang Yang, one of the study authors. He is a research fellow in the department of neurosurgery at Johns Hopkins University School of Medicine in Baltimore.
An expert who studies health inequities offered one explanation for the findings.
"Disparities in health outcomes will always occur as long as people have disparities in their social support systems," said Christine Spencer, interim dean at the Yale Gordon College of Arts and Sciences at the University of Baltimore. "If you fear the loss of your job while you undergo treatment, you are less likely to agree to the invasive, debilitating but necessary treatments that cure cancer."
Dr. Michael Halpern of Temple University in Philadelphia and Dr. Otis Brawley of the American Cancer Society and Emory University in Atlanta say such studies are "a first step" toward erasing disparities in cancer care.
"Adequate health care should be considered an inalienable human right," they wrote in an editorial in the same journal.
For more on cancer treatments, visit the U.S. National Cancer Institute.
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