In the continuing debate over the issue of mammograms, a new Danish study has found that one out of three women with breast cancer detected through mammography is given unnecessary treatment.

The patients did not need treatment because their tumors were slow-growing enough to remain harmless.

In recent years, research showing that mammograms lead to overdiagnosis has sparked controversy on the popular breast cancer screening, with the American Cancer Society and other groups changing their recommendations on when and how often screening should be done. In Europe, for instance, the Swiss Medical Board now advises against getting routine mammograms.

More Small, Early-Stage Tumors Detected

In the latest related study discussed in the Annals of Internal Medicine, researchers warned of detecting and treating small growths that are not likely to progress into cancer — and missing dangerous tumors that develop into advanced cancer — through mammograms.

Dr. Karsten Jorgensen, Rigs Hospitalet professor and Nordic Cochrane Center chief, mourned that the rate of late-stage cancers is still on the rise.

“So the screening doesn’t seem to be working in the way we thought it would. The screening isn’t picking up the cancer it’s supposed to pick up,” Jorgensen said.

The Danish team estimated overdiagnosis rate through a comparison of the number of early-stage and advanced breast tumors before and after Denmark began offering mammograms. If the screening is doing its job, the number of small, curable breast tumors should climb while the large ones should be reduced by around the same amount.

Mammograms in the country found a lot more breast cancer cases, but mostly smaller lesions. Advanced cancers, however, did not fall in numbers.

It is possible for the advanced cases to grow quite rapidly that they pop up in between screening sessions, Jorgensen observed.

Breast Cancer Screening Today

The likelihood of overdiagnosis and false positives can result in benign growths being tested via biopsy and other tests, prompting a review of the effectiveness of standard screening today.

The new findings raise an important question not exactly on the necessity of screening, but on the effectiveness of current techniques.

Those who believe they are being saved by mammograms could actually be harmed by the cancer screening, which led to treatments like surgery and chemotherapy that they did not really need, said ACS chief medical officer Dr. Otis Brawley in an accompanying editorial.

Throwing its strong support behind breast cancer screenings, the American College of Radiology acknowledges that mammography leads to unnecessary treatment in some instances, but downplays the frequency of such cases.

“The amount of overdiagnosis is really small,” said Commission on Breast Imaging chair Dr. Debra Monticciolo, asserting that these discussions confuse women on how to be screened for the disease.

The ACR recommends yearly mammograms starting age 40, while the U.S. Preventive Services Task Force drew flak in 2009 when it bucked the advice and recommended mammograms every other year starting age 50. In 2015, the ACS also took a step back and recommended annual screenings from 45 to 54, following by testing every other year afterward.

About 253,000 new breast cancer cases are expected to be diagnosed in the United States this year, with almost 41,000 deaths.

A separate 63,000 females will be diagnosed with ductal carcinoma in situ, which maintains some cancer traits and whose cells appear malignant but not seeming invasive of surrounding tissue.

Some experts have called for merely considering DCIS a risk factor given it poses a low risk.

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