MedicalResearch.com Interview with:
Diana L. Miglioretti, PhD
Dean’s Professor in Biostatistics
Department of Public Health Sciences
UC Davis School of Medicine
Davis, CA 95616
Medical Research: What is the background for this study? What are the main findings?
Dr. Miglioretti: Screening mammography intervals remain under debate in the United States. The US Preventive Services Task Force recommends biennial (every other year) screening, whereas other organizations recommend annual screening. To help inform their updated screening guidelines, the American Cancer Society guideline development group requested that the US Breast Cancer Surveillance Consortium conduct a study comparing cancer outcomes among women screened annually vs. biennially. Prior studies conducted by the consortium used wide intervals for defining annual and biennial mammograms. We wanted to evaluate cancer outcomes for women who more closely adhere to screening intervals. Our goal was to determine if women diagnosed with cancer following biennial screening have tumors with less favorable prognostic characteristics compared to women diagnosed after annual screening. We evaluated outcomes separately by age and by menopausal status because evidence suggests that younger women and premenopausal women may have more aggressive tumors and thus may benefit from more frequent screening.
We found from this study that premenopausal women diagnosed with invasive breast cancer following biennial versus annual screening mammography were more likely to have tumors with less-favorable prognostic characteristics (e.g., later stage, larger size). For example, women with an invasive breast cancer diagnosed after a biennial screen had a 28% increased risk of a stage IIB or higher tumor, a 21% increased risk of being diagnosed with a tumor >15 mm, and an 11% higher risk of being diagnosed with a tumor with any less-favorable prognostic characteristic compared women diagnosed with breast cancer following an annual mammogram.
In contrast, we found postmenopausal women not using hormone therapy and women 50 years of age or older had similar proportions of tumors with less-favorable prognostic characteristics regardless of screening interval. Relative risk estimates were close to one with no significant differences between biennial and annual screeners.
Among postmenopausal women using hormone therapy at the time of the mammogram and women age 40-49, results were less clear. Relative risk estimates for biennial versus annual screeners were consistently above one, but were not as large as for premenopausal women and were not statistically significant.
Medical Research: What should clinicians and patients take away from your report?
Dr. Miglioretti: Our study has implications for breast cancer screening guidelines and for women and their physicians making decisions about how often to screen for breast cancer. Our results suggest that menopausal status may be more important than age when determining screening intervals. Our results also suggest than post-menopausal women may want to be screened every two years given there is no greater risk of being diagnosed with an advanced cancer and potential harms are reduced with biennial compared to annual screening. In contrast, premenopausal women who choose to be screened may want to be screened annually to increase their chances of a cancer being diagnosed at an early stage; however, the potential benefit of more frequent screening should be weighed against the increased potential for harms such as false positive recalls and biopsies, which are 1.5 to 2 times higher in annual versus biennial screeners.
Medical Research: What recommendations do you have for future research as a result of this study?
Dr. Miglioretti: Future research should continue to identify risk factors that impact the benefits and harms of screening so we can move towards a more personalized screening approach in terms of when to start and stop screening, how often to be screened, and which modalities to use. Our ability to quickly and efficiently conduct this study at the request of the American Cancer Society was made possible because of research infrastructure support for the Breast Cancer Surveillance Consortium. Through ongoing research, the BCSC data will continue to provide new insights into how we can tailor screening recommendations to ensure women have the greatest opportunity for early breast cancer detection while keeping call-backs and other potential harms of the screening process to a minimum.
Diana L. Miglioretti, PhD (2015). Should Breast Cancer Screening Be Different For Pre vs Post Menopausal Women?