Researchers at Case Western Reserve School of Medicine in Cleveland reviewed data for 31,957 patients treated for melanoma between 1996 and 2009 in Ohio.
They found that patients were two and a half times likelier to be diagnosed with late-stage melanoma if they were covered by Medicaid, said lead author Katherine Chiang, a fourth-year medical student at Case Western.
In the final study, researchers found that Chicago women were less likely to receive medically advanced techniques for diagnosing breast cancer if they had Medicaid or Medicare, the government insurance program for older Americans.
Only 47 percent of Medicaid or Medicare patients received a breast MRI, compared with 81 percent of those with private insurance, researchers found.
Image-guided core needle biopsy, which uses imaging scans to guide the needle to the site of the suspected cancer, had similar utilization differences -- 25 percent of Medicaid or Medicare patients received this test, compared with 81 percent of patients with private insurance.
The reasons behind the poorer cancer care for Medicaid patients are complex, ASCO spokespeople said.
Patients often have trouble finding a doctor or hospital that participates in Medicaid, because the program traditionally has not paid as well as Medicare or private insurance for medical services, said Patel and Dr. Harold Burstein. He is an ASCO spokesman and an oncologist with the Dana-Farber Cancer Institute in Boston and an associate professor at Harvard Medical School.
On top of that, Medicaid's low-income enrollees have life problems that can hamper their cancer care, such as being unable to get a ride to the doctor or to leave work for an appointment, Patel and Burstein added.
Medicaid patients also tend to have more health problems overall, which means they may put off cancer screening to focus on chronic illnesses like heart disease or diabetes, Chiang noted.
More people than ever are covered by Medicaid or the Children's Health Insurance Program, with 4.8 million additional people joining since the Affordable Care Act marketplaces opened in October 2013. Currently, a total 64.6 million low-income people are covered by the federal health insurance programs.