LAS VEGAS (KLAS) — A new study should give doctors and women more confidence when it comes to their annual mammograms. Mammography screening can sometimes lead to overdiagnosis but there wasn’t a lot of agreement on how often it actually happens.

What’s at issue is finding non-progressive cancer that in a women’s lifetime would not have caused symptoms or problems but it’s treated anyway.

This new study shows it happens to about one in seven women. 

“These sorts of studies are very very important,” said Dr. Russell Gollard.

He is the medical director for Optum Care Cancer Center. He knows if a clinician finds cancer on a mammogram it often triggers a slew of follow-up treatment.

The surgeries, the chemotherapy, and the hormonal therapy.

But if it’s a silent indolent tumor, the patient could undergo a barrage of unnecessary procedures. It’s hard to tell the difference between something harmless and something harmful.

“So looking at an individual woman and saying your cancer is non-progressive versus is it something that may take away years of your life or cause a disfiguring illness, that’s what’s really difficult to do,” Dr. Gollard said.

That presents a trade-off to screening that can only really be understood if researchers know how often overdiagnoses occur. 

“About one in 1,000 women who undergo mammography will have found cancer that would have never caused problems,” he said.

That’s roughly 15%. That new estimate comes as a relief to breast cancer clinicians, who say the study should reinforce the idea that the benefits of mammography generally outweigh its risks.

“So the important thing is the balance. Early diagnosis sure but the right amount of treatment,” Gollard said.

It’s very nuanced and requires a thoughtful conversation between the patient and her doctor.