A 65-year-old patient gets a mammogram

A 65-year-old patient gets a mammogram (Heather Charles, Chicago Tribune / April 2, 2012)

The findings don't mean that mammography is never worth it, Kalager said, and there's evidence it does save some lives.

Dongfeng Wu, who models cancer screening at the University of Louisville, said that her own research has suggested the rate of overdiagnosis is generally lower, at about six to nine percent instead of up to 25 percent.

That's based on estimates of how accurate mammography is, as well as how long it typically takes breast tumors to become symptomatic.

Even with a lower chance of unnecessary diagnosis and treatment, some women may choose to opt out of mammography, said Wu, who wasn't involved in the new study.

"If a woman thinks she has a higher risk because of her family — close relatives have breast cancer — she might want to (get screened) regularly," Wu told Reuters Health.

"Or if she considers herself a low-risk person, she might just do it every few years, or she might just skip it."

The researchers agreed that once women have all the relevant information, they should be allowed to make their own decision on screening without judgment.

"Women are told about the benefits, but not about the harms," Kalager said. "They are really misinformed."

The harms of cancer screening are the subject of debate. They can range from anxiety to further invasive and expensive testing and treatment.

The authors of a linked commentary wrote that doctors "have an ethical responsibility to alert women to this phenomenon."

Dr. Joann Elmore from the University of Washington School of Medicine and Dr. Suzanne Fletcher of Harvard Medical School added, "Most patient-education aids do not even mention overdiagnosis, and most women are not aware of its possibility."

"There's no right answer here except: tell people the truth," Welch told Reuters Health.

"Rational women can look at the data on mammography and come to different conclusions. I think there's a genuine choice here."

SOURCE: http://bit.ly/atTzv0 Annals of Internal Medicine, online April 2, 2012.