NEW ORLEANSFox Chase Cancer Center investigators presented further support for yearly mammograms in women age 40 and older at the 44th Annual Meeting of the American Society for Therapeutic Radiology and Oncology (ASTRO abstract plenary 2).
In this study involving 1,591 women, those who underwent screening mammography at least annually were more often diagnosed with noninvasive stage 0 breast cancer than women with less frequent or no prior screening. Women with any history of mammography screening prior to diagnosis also presented with earlier stage invasive disease and smaller tumor size, which led to a greater likelihood for breast-conserving surgery, reported lead author Gary M. Freedman, MD, of Fox Chase Cancer Center.
Additionally, in the subset of women aged 40 to 49, for whom screening has been more controversial, screening was significantly associated with lower tumor stage and smaller tumor size, Dr. Freedman said.
Women age 40 and older were included if they had newly diagnosed breast cancer and were able to supply information about the number and frequency of their mammograms prior to their breast cancer diagnosis.
Study participants were classified into three groups: Group 1 (unscreened) had never had a mammogram prior to diagnosis; group 2 (partially screened) had mammograms on average less than once a year; and group 3 (highly screened) had mammograms on average yearly or more often. These three groups were compared for method of detection, T stage at diagnosis, tumor size, and eligibility for breast conservation. For each patient, a mammogram frequency index was assigned by a formula: frequency = age minus 40/number of prior mammograms.
The method of cancer detection was by mammogram alone in 33% of group 1 patients, 49% of group 2 patients, and 59% of group 3 patients. Ductal carcinoma in situ (DCIS) was diagnosed in 15% of group 1 subjects, compared with 21% in group 2 and 26% in group 3 (P < .0001), Dr. Freedman reported.
Of the unscreened patients, 32% had stage T1 disease, compared with 53% of patients in both screening groups. In addition, the tumor size was 1 cm or less in 8% of unscreened women, compared with 22% of screened women (P < .0001).