Medicaid expansion under the Affordable Care Act (ACA) may have helped extend the lives of more US women with breast cancer, a large, long-term study finds.

In the years since US states began expanding Medicaid eligibility under the 2010 ACA, studies have pointed to benefits for patients with cancer, including earlier diagnosis and better access to treatments.

The new study, published in JAMA Network Open, suggests that those gains have translated into improved long-term survival for women with breast cancer. Among more than 1.5 million US women diagnosed with breast cancer between 2006 and 2021, those living in Medicaid-expansion states saw an absolute reduction in overall mortality of 1.4 percentage points over 5 years, compared with women in non-expansion states.

That difference corresponds to about 1400 deaths averted for every 100,000 patients who gained coverage under Medicaid expansion.

“Our message is, Medicaid expansion is associated with life-saving measures. It saves lives,” said lead researcher Oluwasegun A. Akinyemi, MD, PhD, a senior research fellow at Howard University College of Medicine in Washington, DC.

While some previous research has linked Medicaid expansion to longer survival among women with breast cancer, the new study is notable for its size and length of follow-up, according to an accompanying editorial.

“The fact that this was able to show over the course of over a decade that Medicaid expansion had a durable effect is something that is novel,” said editorialist Oluwadamilola Fayanju, MD, chief of the Division of Breast Surgery at Penn Medicine in Philadelphia.

The findings also come at a critical time, Fayanju told Medscape Medical News. “This certainly is a timely manuscript, given multiple things happening in the changing American healthcare landscape,” she said.

Last July, the “One Big Beautiful Bill Act” was signed into law, with plans to cut over a trillion dollars in federal Medicaid spending over 10 years, which will result in nearly 15 million Americans losing their coverage, according to Congressional Budget Office estimates.

Patients with cancer “will almost certainly” experience treatment delays as a result, Fayanju and colleague Meghan Maceyko, MD, wrote — and it will be those from marginalized groups who are most affected.

“We often see that the people who are most vulnerable in a society are the ones most likely to suffer an adverse effect,” Fayanju said. “That will have [an] impact not only on the individuals [and] their families but potentially also on their communities.”

Healthcare systems will pay a price, too, the editorialists noted: They will “bear the financial burden” of interruptions in care caused by patients’ loss of coverage and increases in later-stage cancer diagnoses due to declines in screening.

For their study, Akinyemi’s team analyzed data from a National Cancer Database cohort of over 1.5 million women who were diagnosed with breast cancer between the ages of 40 and 64 years.

Overall, 58% lived in Medicaid-expansion states — defined as states that expanded eligibility between 2010 and January 2014. The rest lived in non-expansion states, defined as those that had not implemented expansion at the time of the dataset release. States that expanded Medicaid eligibility after January 2014 were excluded from the analysis.

The researchers found that between 2006 and 2013, there was no difference in mortality trends between patients with breast cancer in expansion and non-expansion states. That changed post-ACA implementation: Medicaid expansion was associated with a modest but significant reduction in overall mortality (hazard ratio, 0.95; P < .001), in models adjusted for factors such as race/ethnicity, zip-code-level income, education level, and initial treatment type.

“The policy saves life,” Akinyemi said. “And it saves it irrespective of your disease stage, your race, your income, or even the treatment modalities that you received.”

Even so, the researchers did find that survival gains were particularly pronounced among Hispanic patients, who experienced a 19% relative reduction in mortality associated with Medicaid expansion.

That, Akinyemi said, might be because a particularly large proportion of Hispanic individuals lacked insurance prior to the ACA.

Meanwhile, the relative mortality reduction associated with Medicaid expansion was less for non-Hispanic Black women, at 4.3%. That finding highlights persistent inequities that insurance coverage alone may not fully address, according to Akinyemi’s team.

More work is needed, they wrote, to see whether additional policy measures can help close the gap between Black women and other historically marginalized groups.