A bill requiring health plans to cover digital breast tomosynthesis, a three-dimensional type of mammography, has been delivered to Governor Andrew Cuomo’s office for his signature or veto. If the measure is enacted into law, it would be a classic case of healthcare politics rushing ahead of medical science.

Clinical studies have found that 3-D mammograms do a better job of finding potential tumors, especially in the roughly half of women with dense breast tissue, and in avoiding false positive results.

However, the U.S. Preventive Services Task Force has declined to recommend the procedure, citing a lack of long-term research to show that the procedure—which uses a higher dose of radiation than traditional mammography—would lead to better health outcomes.

“The USPSTF concludes that the current evidence is insufficient to assess the benefits and harms of digital breast tomosynthesis (DBT) as a primary screening method for breast cancer,” the agency said in a recommendation published last year.

Despite the scientific uncertainty, Memorial Sloan Kettering Cancer Center and other providers have pushed Albany to mandate insurance coverage for the procedure.

The Cuomo administration responded in February by announcing that it was issuing regulations requiring health plans to cover 3D tomosynthesis “when medically necessary.”

Meanwhile, legislation to impose a broader mandate was introduced by Assemblywoman Rebecca Seawright, D-Manhattan, and Senator Joseph Griffo, R-Rome. Their bill requires coverage of breast tomosynthesis to same extent as traditional mammograms—meaning plans must pay for one “baseline” screening between ages 35 and 39, then at least annual imaging after that.

Because the bill omits mention of medical necessity, plans could not limit the procedure to women with dense tissue, family histories of breast cancer or other risk factors.

The New York Health Plan Association warned that the additional tomosynthesis mandate would increase its members’ costs—and consumers’ premiums—without any demonstrated benefit for patients.

“3-D digital mammography is significantly more expensive than traditional mammography, and there is no evidence to show that 3-D digital mammography should replace traditional mammography as the frontline screening for breast cancer,” the association said in a memorandum of opposition.

Still, the Seawright-Griffo bill passed the Assembly in March and the Senate in June without a single “no” vote. The Legislature formally delivered the bill to Cuomo’s office last Friday, giving him until November 29 to take action.

The bill fits an Albany pattern of imposing coverage mandates based on lobbying by provider or patient groups, but without consulting independent experts. The Legislature voted in 2009 to establish a Health Care Quality and Cost Containment Commission to analyze the costs and benefits of such proposals. But officials never followed through on appointing the panel, and Cuomo eliminated its unused budget earlier this year.

Even for traditional mammograms, New York’s law goes well beyond the recent guidelines of some experts. The Preventive Services Task Force recommends routine screening for women at average risk only every other year from 50 to 74. Noting the downsides of over-diagnosis and unnecessary treatment, the panel says the decision to screen earlier than 50 should be “an individual one”: “Women who place a higher value on the potential benefit than the potential harms may choose to begin biennial screening between the ages of 40 and 49 years.”