Study Finds Annual Mammograms Associated With Lower Risk of Late-Stage Breast Cancer
The study authors suggest that annual screening for women aged 40 and older may be beneficial, but warn of the increased risk of false positive results.
Research published in the Journal of Clinical Oncology shows that women who are diagnosed with breast cancer who had regular screening mammograms every year were less likely to have late-stage cancer. Additionally, these patients also had higher overall survival (OS) compared with those who received screenings every other year or less often.1
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Prior clinical trials have demonstrated benefits of mammography screening for breast cancer; however, guidelines differ on how frequently women should be screened. For example, the American College of Radiology—as well as other organizations—suggest that annual screening should begin after 40 years of age, whereas the US Preventative Services Task Force suggests biennial screening from age 40.1
For this study, the authors assessed the rate of late-stage cancer and OS for different breast cancer screening intervals. Real-world institutional data were used and included 8145 patients who had both a cancer registry record of new breast cancer diagnosis and prediagnosis screening history between 2004 and 2019. Time interval between the 2 screening mammograms immediately preceding diagnosis and time to cancer diagnosis were determined, and screening interval was considered annual if time between intervals was 15 months or less, biennial if between 15 and 27 months, and intermittent if greater than 27 months or if 1 prediagnosis screening was known.1,2
The study’s primary end point was late-stage cancer (defined as TNM stage IIB or worse) and the secondary end point was OS. The association of screening interval and late-stage cancer was analyzed and adjusted for prediagnosis characteristics if necessary. Additionally, the authors note that potential lead time was analyzed using survival from a uniform fixed time point.2
The results indicated a significant increase in the frequency of late-stage cancers that were diagnosed in the increasing screening intervals, with annual, biennial, and intermittent groups demonstrating 9%, 14%, and 19% of late stages, respectively. The investigators note that this trend was present regardless of the patients’ age, race, and menopausal status.2
“The percentage of late-stage cancers increased significantly with increased screening intervals,” said lead author Margarita Zuley, MD, professor and chief of the division of breast imaging in the Department of Radiology at the University of Pittsburgh and UPMC, in a news release. “Annual mammograms are crucial for early detection of breast cancer, which increases the likelihood of survival, decreases harm to patients because treatment may not need to be as intense, makes recovery easier, and can lower the cost of care.”1
Additionally, the findings demonstrated that biennial and intermittent groups had noticeably worse OS than those who were screened annually (biennial: HR 1.42 [95% CI, 1.11-1.82]; intermittent: HR 2.69 [95% CI, 2.11-3.43]). This changed to 1.39 (95% CI, 1.08-1.78) and 2.01 (95% CI, 1.58-2.55), respectively, following adjustment for potential lead time.2
The investigators noted that with more frequent mammograms, there is an increased risk of false positives that may lead to unnecessary biopsies and anxiety. Another recent study published in Annals of Internal Medicine found that women who had received false positive test results during breast cancer screenings and who needed additional imaging or biopsies to confirm the findings were less likely to attend follow-up screenings. Of over 3.5 million screenings evaluated in this study, 3,184,482 were deemed “true negatives” and 345,343 were considered to be false positives.1,3
“It’s important to understand that most women recalled for additional imaging due to a finding on a screening mammogram do not have breast cancer,” said lead author Diana Miglioretti, PhD, cancer center researcher and chief of the Division of Biostatistics at UC Davis, in a news release. “They should try not to be worried if they are recalled for additional work-up. It is a normal and common part of the screening process.”3
These false positive results are somewhat common, with approximately 10% to 12% of mammograms in women aged 40 to 49 years being affected. False positives are also notably common in younger women. Further, after 10 years of annual screenings, about 50% to 60% of women can expect to receive at least 1 false positive, and 7% to 12% at least 1 false positive with the recommendation to receive a biopsy. In addition, approximately 10% of the time, any additional imaging is performed to get a better look at what the mammography might find.1,3
Of the women who received false positive results, only 61% returned for their mammogram within 6 months, and 67% returned for a biopsy. The study also found that women who received 2 screening mammograms within 5 years who had a false positive result on their second were less likely to return for a third screening, regardless of the result during the first screening.3
“We recognize that there are potential harms associated with calling women back for additional screening, but I don’t think that these harms outweigh the risk of missing cancers and women dying as a result,” said Zuley in the news release. “We’re also working on testing screening tools that have lower false positives than mammography and pushing on every front to identify the most cost-effective and accurate way of taking care of our patients.”1
Although somewhat common, these false positives may have financial implications for patients as well as cause increased emotional stress or anxiety, the authors noted. For those who feel anxious about waiting for screening mammography results, they may be able to request on-the-spot interpretations of the mammogram in some facilities. Additionally, others may offer the service in addition to a same-day diagnostic work-up if a suspicious finding is discovered. Additionally, the authors urged health care professionals to explain false positive results to their patient, reassure them that a result may be negative, and stress the significance of continued screenings.3
“Only about 65% of women over age 40 are screened for breast cancer, and only about half of those women are getting annual screening—in part because of conflicting guidelines about recommended screening intervals,” said Zuley in the news release. “Our study shows that there is a significant benefit for annual screening over biennial screening, including in premenopausal women.”1
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