Cancer deaths have dropped more in states that expanded Medicaid coverage under the Affordable Care Act than in states that did not, new research reveals.

The report Wednesday is the first evidence tying cancer survival to the health care change, which began in 2014 after the law known as “Obamacare” took full effect, said one study leader, Dr. Anna Lee of Memorial Sloan Kettering Cancer Center in New York.

“For a policy to have this amount of impact in a short amount of years” is remarkable, because cancer often takes a long time to develop and prove fatal, she said.

Lee discussed the results in an American Society of Clinical Oncology news conference as part of its annual meeting later this month.

The law let states expand Medicaid eligibility and offer subsidies to help people buy health insurance. Twenty-seven states and Washington, D.C., did that, and 20 million Americans gained coverage that way. The other 23 states did not expand benefits.

Researchers used national health statistics on cancer deaths to track trends before and after the law. They looked only at deaths in people under 65, who stood to benefit from the change because those older already were covered by Medicare. About 30% of U.S. cancer deaths are in people under 65.

The cancer death rate fell throughout the United States from 1999 to 2017 in that age group, but more in states that expanded Medicaid — 29% versus 25% in states that did not.

Researchers specifically compared death rates from 2011 to 2013, before the health care change, to 2015 to 2017, after it. In states that expanded coverage, the change meant 785 fewer cancer deaths in 2017. Another 589 deaths could have been prevented that year if all states had expanded Medicaid, researchers estimated.

Having health insurance allows quicker treatment after diagnosis and access to more treatment options so patients can get the best care available, which can improve survival odds, Lee said. Insured people also may have more opportunities for screening to detect cancers at a stage when they’re most treatable.

The new work builds on research from last year’s conference that suggested more patients, blacks in particular, were able to quickly start on treatment after a diagnosis of advanced cancer in states that expanded Medicaid, said Dr. Howard Burris. He is president of the oncology society and heads the Sarah Cannon Research Institute, a cancer center in Nashville, Tennessee.

“There was so much excitement” when federal statistics showed a big drop in cancer deaths over the last decade, and the new study shows “it was an even better improvement in expansion states,” said Burris, who had no role in the study.

The picture is murky for specific racial groups. States that expanded Medicaid generally had fewer blacks and more Hispanics than states that did not expand. Blacks have had worse cancer death rates than other groups, but that also has been improving at a greater rate than for whites. Expansion of Medicaid seemed to make no difference in cancer mortality rates for blacks, but did seem to improve the situation for Hispanics.

To date, 36 states and Washington, D.C., have expanded Medicaid and 14 have not.