WASHINGTON (WUSA9) -- New questions being raised about the value of routine screening mammograms.

Instead of reducing the incidence of advanced cancers, Danish researchers find breast screenings lead to a substantial over diagnosis of small breast tumors that may never affect the patient’s health during a life time. The study is published in the January 10th issue of the Annals of Internal Medicine.

A mammogram does not prevent breast cancer, but it can help find breast tumors at the earliest most treatable stage. However, new research finds that leads to overdiagnosis.

Data from two comprehensive Danish registries find that screenings equaled a substantial increase, about one-in-three, in the detection of small tumors that might never affect a patient's health over a lifetime. But screening was not associated with a reduction in advanced tumors.

Sara Bruce, MD is a Breast Surgeon at Inova Alexandria Hospital. She stresses that mammography remains the best tool that we have to catch breast cancer early, while the disease is potentially curable. Although not perfect, mammograms are responsible, in part, for the 30 percent reduction in death from breast cancer that we have seen in the U.S. over the last 25 years.

"The problem is we don't have any way to detect at this point whose early cancer is worse than someone else who's more in need of treatment and so we really end up treating everyone to prevent those that could potentially become worse," said Dr. Bruce.

The problem with overdiagnosis of non-advanced tumors is it unnecessarily exposes patients to the potential harms of surgery, chemotherapy and radiation without any clinical benefit.

Otis Brawley, MD is the Chief Medical Officer of the American Cancer Society. He suggests that it's time for the everyone to acknowledge through existing studies that overdiagnosis of breast cancers due to mammography screenings do indeed exist.

Dr. Brawley says, "Somewhere around 15 to 20 percent of localized breast cancers are likely overdiagnosis."

He believes the focus should be on preventing breast cancer through diet, weight control, exercise and knowing your own personal risk factors. But the findings do not mean that screening should be abandoned.

"If we are aware of the limitations of mammography, it helps us to use mammography better so that we can help the most people. It also stimulates support for research which can find something better than mammography," said Dr. Brawley.

Dr. Brawley adds the 21st century screening approach will involve genomics along with biopsy, instead of biopsy alone.