Overweight women might need mammograms more often because being overweight increases the risk that a tumor will become large before it is detected, researchers from Karolinska Institutet in Sweden argue in a study they will present at the Radiological Society of North America (RSNA) 2017 Scientific Assembly and Annual Meeting.

Since larger tumors are linked to worse prognosis, more frequent check-ups may improve the chances of better outcomes.

The data may provide guidance to physicians advising their patients on breast cancer screening, and might influence changes in screening guidelines.

The study, which included 2,012 women with invasive breast cancer, was looking for factors making it more likely that detection was offset until the tumor was larger than 2 cm (0.8 inches). The size was not chosen at random. Researchers know that once a tumor passes this size, it goes from a stage 1 to stage 2 cancer, and is linked to a poorer prognosis.

In addition to body mass index (BMI), researchers studied the impact of breast density. They discovered that for tumors detected at the mammogram screening, higher BMI and breast density were linked to larger tumor sizes.

For cancers detected between the two-year screening intervals, only BMI was linked to larger tumors. And while breast density was not linked to disease progression in this group of patients, women with higher BMI had a worse prognosis than those with lower weights.

“Our study suggests that when a clinician presents the pros and cons of breast cancer screening to the patient, having high BMI should be an important ‘pro’ argument,” Fredrik Strand, MD, a radiologist at the Karolinska University Hospital and a study co-author, said in a press release.

“In addition, our findings suggest that women with high BMI should consider shorter time intervals between screenings.”

Larger tumor size, however, is not the only factor influenced by a higher BMI. Overweight women also may have specific molecular tumor characteristics and hormone receptor levels that make tumors harder to treat.

In Sweden, current screening recommendations state that women should have mammograms every 18 to 24 months. The team noted that is longer than the 12 months endorsed by many U.S. organizations, including the American Cancer Society. But it is in line with the 24 months recommended by the U.S. Preventive Services Task Force.

Sweden, however, has fewer overweight women than the U.S., the team noted.

While Strand’s immediate goals are a direct extension of the current study — exploring how breast density impacts detection — his longer-term goals are more ambitious.

He wants to learn to harness the power of artificial intelligence to personalize screening programs based on known breast cancer risk and the likelihood of detecting a tumor — taking a step away from generalized recommendations.