Missed mammograms represent missed opportunities for early breast cancer diagnosis, a study involving Marshfield Clinic and the University of Wisconsin-Stevens Point’s Geographic Information Systems (GIS) Center showed.

The two organizations have partnered since 2010 to discover what causes missed mammograms.

Women who undergo annual mammograms and are diagnosed with breast cancer are more likely to have earlier-stage disease at diagnosis than women who aren’t examined yearly, the study found. It was led by Adedayo Onitilo, M.D., Marshfield Clinic oncologist/hematologist.

Dr. Onitilo’s research team partnered with the GIS Center’s Doug Miskowiak to study patient and clinical characteristics that lead to missed mammograms. They include family history of breast cancer, number of medical encounters and — notably — travel time to screening facilities.

“This study shows that travel distance to the nearest mammography center is an important barrier to routine breast cancer screening,” said Miskowiak, GIS education specialist at UW-Stevens Point. Each additional minute of travel time decreased the odds of undergoing at least one mammography examination in the five years before cancer diagnosis.

Women who missed five of their last five mammograms lived twice as far from the nearest mammogram facility as those who missed none. “Thirty minutes of travel time seems to be the turning point,” Miskowiak said.

Marshfield Clinic, an early innovator of electronic health records, has a vast set of patient data. The GIS team converted addresses to data points and used a road network to analyze travel time between where patients live and where they receive care.

Analyzing patient geographic characteristics reveals patterns and trends.  “We found that geography makes a difference in human health outcomes. Reducing geographic barriers — by maximizing the use of mobile mammography units, for example — may improve patient access to health care, Miskowiak said.

The study, which was published in the prestigious American Journal of Roentgenology in November, has received international attention.

Funded by Marshfield Clinic Research Foundation, it involved data from 1,300 patients prior to 2008. The research team is seeking funding for a subsequent study of 13,000 patients from 2008 to 2012.

“Our results confirmed our suspicion that missed annual mammograms, particularly for younger women, may be associated with higher-stage breast cancer at diagnosis,” Dr. Onitilo said. “Women who had not undergone mammography screening in the year before diagnosis were 12 percent as likely as those who had mammograms to be diagnosed with late-stage breast cancer.”