Breast cancer experts are calling for a fresh look at routine mammography, warning that screening may not save lives and may instead lead to risky overdiagnoses.
In a pair of editorials published in the Annals of Internal Medicine, researchers cited extensive new data that suggests that mammograms provide no life-saving benefit compared with regular breast exams and routine care. The new findings, taken from two 25-year Canadian National Breast Screening Studies, cast doubt on older trials that made a strong case for routine mammography.
One editorial came from a pair of researchers in Switzerland who called for a new type of breast cancer screening trial, saying that older studies that form the foundation of modern practice are riddled with bias. Trials without randomization and blinding have almost invariably reported lower rates of breast cancer mortality for patients who were screened, but that may be tied to physicians’ leanings in how to categorize other causes of death.
"Were the small reductions in breast cancer deaths afforded by screening in published trials not only diluted but canceled out by deaths from other causes? Should we get accustomed to the possibility that mammography screening does not really save lives?" asked authors Dr. Peter Jüni and Marcel Zwahlen of the Institute of Social & Preventive Medicine in Bern, Switzerland. "Endless rehashing of data from old trials cannot provide definitive answers to these questions. The only way to know for certain is to initiate a new trial in the era of contemporary screening technologies and breast cancer therapies."
In a separate editorial, Dr. Russell Harris called for renewed focus on prevention rather than detection of breast cancer. About 40,000 women die each year from breast cancer, many more are diagnosed with the disease and even more have had a false-positive mammogram, said Harris, who works at the Sheps Center for Health Services Research at the University of North Carolina.
Harris called the Canadian studies a spotlight on the need for "contention and caution in tying our hopes to screening as the panacea for reducing the burden of breast cancer," saying that, at best, mammography makes little difference in saving lives that might be lost to breast cancer.
What does that mean for women navigating the thorny issue? Harris says it’s a matter of re-framing the healthcare focus on prevention.
"If we can come to think of screening in a more limited way, moving some of our hope to lifestyle change, we could potentially reduce the harms of screening and gain the multiple benefits of a healthy lifestyle," he wrote. "Maybe it would even lessen the contentious mammography debates and give a new meaning to the ‘race for the cure.’ We just need to think and hope in a different way."
Both editorials were spurred by results from the pair of Canadian National Breast Screening Study (CNBSS) trials, launched in 1980 and followed for 25 years. One study concluded that annual mammography paired with clinical breast examination for 4-5 years did not reduce breast cancer deaths compared with minimal screening, defined as a 1-time clinical breast exam. The 2nd concluded that mammography plus CBE made no difference compared with CBE alone in women aged 50 to 59.
Furthermore, the CNBSS results suggest that about 22% of screen-detected breast cancers were "over-diagnosed," meaning they were diagnosed with and treated for breast cancers that would not have led to their deaths.
"The bottom-line messages of CNBSS are that mammography probably adds little to reducing breast cancer deaths for women aged 40 to 59 years but may add more for women aged 60 to 69 years," Harris wrote. "Also, the harms of over-diagnosis are substantial, giving us further pause about the wisdom of screening mammography. If we hear the messages, we may begin to witness the slow scaling back of what has been our greatest hope for reducing the burden of suffering due to breast cancer: screening mammography."
The arguments add to the ongoing controversy, sparked largely in 2009, over the proper use of mammography and its potential role in routine care.
The U.S. Preventative Services Task Force altered its mammogram recommendations in 2009 to advise that women under the age of 50 who aren’t at increased risk of developing breast cancer may not need routine screening. The agency, an independent body funded by the U.S. Dept. of Health & Human Services, further recommended mammograms only every 2 years for women aged 50 to 74.
The USPSTF recommendation was in harmony with guidelines from the Health Organization and the American Academy of Family Physicians, but the American Medical Assn. balked at the guidance, urging all women over the age of 40 to submit to yearly mammograms. The Mayo Clinic agreed.
The debate has raged on, with varying bodies warning that the risks of screening and the dangers of false positives must be taken into account when advising patients to undergo mammography. Some groups have warned that missed mammograms could mean missed cancers while others have criticized groups such as breast cancer charity Susan G Komen for the Cure for overstating the benefits of mammography while ignoring the risks.
In his new editorial, Harris agreed with the USPSTF recommendation for biennial mammography in women aged 60 to 69, saying it "may provide the best trade-off between benefits and harms."