Annual screening mammography lowers the risk of late-stage cancer

Annual screening mammography is superior to biennial screening in reducing the risk of late-stage breast cancer detection and overall mortality, according to an observational study published in the Journal of Clinical Oncology.¹

Based on data from a cancer registry of 8145 patients with either a new breast cancer diagnosis or a prediagnosis screening history between 2004 and 2019, the study found that the percentage of late-stage cancers (defined as TNM stage IIIB or worse) significantly increased as the screening interval lengthened between mammography screenings. Late-stage cancers were found in 9% of patients undergoing annual mammography (interval ≤15 months), in 14% of those undergoing biennial mammography (≤27 months), and in 19% of those undergoing intermittent mammography (>27 months).

The findings were consistent regardless of age, menopausal status, or race. Mortality also was lower with annual mammography, with substantially worse overall survival seen with biennial and intermittent screening (relative hazards of 1.24 and 2.69, respectively).

The lead author of the study, Margarita L. Zuley, MD, chief of the Division of Breast Imaging in the Department of Radiology at the University of Pittsburgh, says that the study was performed to assess the effect of the screening mammography interval on actual patient outcomes because the current assessment is primarily based on modeling studies in the United States. “The study was performed to evaluate if the modeling estimates reflect actual patient outcomes,” she says. “We simply report the results of normal clinical practice, which has evolved over the time period.”

Liane Philpotts, MD, professor of radiology and biomedical imaging at Yale School of Medicine, says that the take-home message of the study is clear. “Annual screening results in a significantly lower risk of advanced or late-stage cancers and the results held for differing age groups, race, and menopausal status,” she says, adding that the findings “support a ‘one size fits all’ recommendation for annual screening for all women aged 40 and up.”

Dr Philpotts notes, however, that the study did not include breast density as a variable, which is linked to both higher breast cancer rates and reduced sensitivity of mammography in detecting breast cancer. This variable is found to be higher in specific ethnicities, particularly Asian women. The study included primarily White women, with only a small number of Asian women included. “Thus, the results of the study may not hold true for all ethnicities when density is also taken into account,” she says.

She also says that further studies will be needed to ascertain whether the advantages of three-dimensional mammography (or digital breast tomosynthesis) in detecting cancers at an earlier stage will translate into the feasibility of longer screening intervals.

The study did not look at outcomes according to the type of mammogram but included women who underwent film screen mammography, digital mammography with and without tomosynthesis, and tomosynthesis with synthetically derived mammography.