The Massachusetts healthcare reform law enacted in April 2006, which required all residents to carry health insurance, did not increase rates of mammography participation, and was not associated with an earlier stage at diagnosis compared with California, according to a study published online July 25 in Cancer.

Previous research had established that uninsured women are less likely than their insured peers to receive preventive care, including mammograms, and are more likely to be diagnosed with breast cancer at a more advanced stage.

Nancy L. Keating, MD, MPH, from the division of general internal medicine at Brigham and Women’s Hospital in Boston, and colleagues, sought to determine whether health insurance expansion was associated with use of mammography and earlier stage at diagnosis in Massachusetts after its healthcare reform.

The researchers mined the Behavioral Risk Factor Surveillance System (BRFSS) and cancer registries in Massachusetts and California. They identified all women ages 41 through 64 years who participated in the BRFSS surveys during 2004, 2006, 2008 or 2010 and identified all women of those ages who were diagnosed with breast cancer from 2005 through 2008. They performed a propensity analysis to inform a comparison among women in California who were most similar to women in Massachusetts.

“Over all study years, women in Massachusetts were more likely to have had a mammogram in the past year (69.7 percent vs. 56.6 percent) or in the past two years (82.6 percent vs. 73.4 percent),” wrote Keating et al.

They also found mammography rates between the two states did not differ in 2008 or 2010, a result that suggests no differences in trends over time after health insurance reform in Massachusetts. When the researchers compared Massachusetts with the rest of the U.S., results were similar. Keating and colleagues did not find any race/ethnicity or income subgroup for which there was an association of mammography by state over time.

Women diagnosed with breast cancer in Massachusetts tended to be slightly younger, more often white, more often married and more likely to be born in the U.S. than Californians. These differences attenuated substantially following propensity matching.

In Massachusetts, the adjusted proportion of women diagnosed with Stage 1 disease increased slightly in 2007 before declining the following year. In California, the adjusted rates of Stage 1 cancer declined slightly over the course of the study.

Although women in Massachusetts had higher rates of mammography use and earlier stage at breast cancer diagnosis than those in California, the researchers could not detect statistically different trends by state to tie the results to healthcare reform in Massachusetts.

Keating and colleagues provided several possible reasons for the findings, explaining that insurance rates were high in Massachusetts prior to health insurance reform. In addition, low-income women had access to free mammography screening pre-reform. Thus, mammography rates had been very high.

They noted that health insurance reform has not improved access to a personal physician in Massachusetts, which may be a barrier to mammography. Costs also may present a barrier, even among insured women, and the deteriorating economic climate may have stalled improvements in 2009 and 2010.

These factors, particularly the low uninsurance rate, also may explain the lack of an association between reform and breast cancer stage at diagnosis.

“Understanding better how health insurance expansion influences mammography use and stage of breast cancer diagnosis in other populations is important and has implications for improving the prognosis for women who develop cancer,” wrote Keating et al, who emphasized the need to assess access to primary care and preventive services in the U.S.