Mammography Has Led to Fewer Advanced-Stage Breast Cancers Being Diagnosed

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Several large studies, including a review by the U.S. Preventive Services Task Force in 2009 and a study on the causes of death in the United Kingdom in 2013, have questioned the value of screening mammograms.

Doctors who question the value of mammograms say that while mammograms do save lives, for each breast cancer death prevented, three to four women are overdiagnosed. Overdiagnosis means either:

  • a screening mammogram finds a suspicious area that would have been eventually diagnosed as cancer by other means, without any effect on prognosis
  • a screening mammogram finds a suspicious area that never would have affected a woman’s health if it hadn’t been found or treated

False positive results from screening mammograms also have helped fuel the debate about the value of breast cancer screening. When a mammogram shows an abnormal area that looks like a cancer but turns out to be normal, it’s called a false positive. Ultimately the news is good: no breast cancer. But the suspicious area usually requires follow-up with more than one doctor, extra tests, and extra procedures, including a possible biopsy. There are psychological, physical, and economic costs that come with a false positive.

These studies and the resulting stories in the media have fueled an ongoing debate about the value of screening mammograms.

A study done by researchers at the University of Michigan has found that in the 30 years since mammography was introduced, fewer advanced-stage breast cancers are being diagnosed.

The research was published online by the journal Cancer on June 24, 2014. Read the abstract of “Reduction in late-stage breast cancer incidence in the mammography era: Implications for overdiagnosis of invasive cancer.”

Researchers looked in the SEER database to find the number of diagnoses of early-stage and advanced-stage breast cancers between 1977 and 1979, before mammography became a standard screening test. They compared these numbers to the number of early-stage and advanced-stage breast cancers diagnosed between 2007 and 2009. SEER databases are large registries of cancer cases from sources throughout the United States maintained by the National Institutes of Health.

The researchers took into account that breast cancer diagnoses were increasing about 1.3% per year. This increase is called an annual percentage change.

It can help to think of the annual percentage change as being similar to the inflation rate: $1 from 1977 doesn’t buy as much in 2007. So just as the cost of money goes up, the number of breast cancer diagnoses is increasing, separate from any efforts to detect the disease earlier.

Using the annual percentage change, the researchers looked at the number of diagnoses in the 1970s and estimated how many early- and advanced-stage diagnoses there would be in 2007-2009. They then compared their estimates to the actual number of diagnoses.

The researchers found that actual advanced-stage breast cancer diagnoses were 37% lower in 2007-2009 than they estimated. Early-stage breast cancer diagnoses increased 48% from 1977-1979 to 2007-2009. This increase corresponded to the decrease in advanced-stage diagnoses.

In the paper, the researchers said that this decrease in advanced-stage diagnoses and increase in early-stage diagnoses is what we would expect to see with a successful screening program. This means mammograms are finding more breast cancers early, when they may be less complicated to treat.

The study also found that since mammography was introduced, there has been an overall 9% decrease in invasive breast cancer. This decrease has been offset by an increase in diagnoses of DCIS (ductal carcinoma in situ), which isn’t invasive.

If you're 40 or older and have an average risk of breast cancer, yearly screening mammograms should be part of your healthcare. If your breast cancer risk is higher than average, you should talk to your doctor about a more aggressive breast cancer screening plan that makes the most sense for your particular situation.

There's only one of you and you deserve the best care possible. Don't let any obstacles, including fear of a false positive, get in the way of your regular screening mammograms:

  • If you're worried about cost, talk to your doctor, a local hospital social worker, or staff members at a mammogram center. Ask about free programs in your area.
  • If you're having problems scheduling a mammogram, call the National Cancer Institute (800-4-CANCER) or the American College of Radiology (800-227-5463) to find certified mammogram providers near you.
  • If you find mammograms painful, ask the mammography center staff members how the experience can be as easy and as comfortable as possible for you.

For more information on mammograms, visit the Breastcancer.org Mammograms page.



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