Abstract
Background/Aims Annual mammogram screening for the early detection of breast cancer in women is recommended by most professional organizations beginning at the age of 40. However, the efficacy of annual mammography screening related to decreasing mortality remains an area of debate due to concerns regarding risk versus benefit. The potential for harm as a result of over-diagnosis of cancers that may not have been clinically significant extends beyond the extensively analyzed breast cancer-specific mortality. Therefore, we sought to examine screening mammography frequency and all-cause mortality in breast cancer patients.
Methods Primary breast cancer cases diagnosed within the Marshfield Clinic system from 2002 through 2008 were identified for retrospective review. Patients diagnosed with breast cancer at another facility, male breast cancer patients, and patients residing outside of Wisconsin and its neighboring states were excluded. Patient demographics and additional data, including number of mammograms performed within five years prior to breast cancer diagnosis, breast cancer stage, insurance status, family history, and comorbidities, were abstracted. Kaplan-Meier curves were generated to assess the association between mammography screening in the five years prior to breast cancer diagnosis and overall survival with adjustment for age, insurance status, number of medical encounters, comorbidities, family history, and calendar year.
Results A total of 1,422 women with breast cancer were included in the analysis. After adjustment, women who missed any of their last five annual screening mammograms had a 2.3-fold increase in all-cause mortality compared to subjects who participated in annual screening mammography. When subjects were stratified by the number of missed screening mammograms in the five years prior to breast cancer diagnosis, a progressive decline in survival was noted resulting in an all-cause mortality hazard ratio of 1.3 (95% confidence interval 1.19 – 1.37, P <0.0001) for each additional missed mammogram.
Conclusions These results suggest that annual mammography prior to breast cancer diagnosis is predictive of increased overall survival. Importantly, a stepwise decline in overall survival was noted for each additional missed mammogram. These results are similar to findings for breast cancer-specific mortality and illustrate the importance of recommending annual screening mammography to all eligible women.
