Abstract P2-01-02: The Incidence of Mammographically-Occult Breast Cancer in Women Older than Seventy Years

Background: Mammographic density generally decreases over time, which increases the sensitivity of screening mammography. However a significant proportion of older women have persistently dense breast tissue. This raises the question of how best to screen older women, particularly those with mammographically dense tissue or other risk factors. Little information exists about the accuracy of screening mammography in women older than seventy years. Additionally, the frequency of older women with mammographically-occult breast cancer is also unknown. The purpose of this study was to report the incidence of mammographicallyoccult breast cancer in women older than seventy and to describe the clinical factors that may be associated with this presentation. Methods: A retrospective chart review was conducted of women older than seventy diagnosed with breast cancer (intraductal carcinoma, invasive ductal carcinoma and invasive lobular carcinoma) at NYU Langone Medical Center from 2002-2009. Data collected included age, presentation, stage, mammographic density, BI-RADS results, breast ultrasound (US) and MRI results, and risk factors. Breast density was categorized according to BI-RADS definitions: 1. predominantly fatty, 2. scattered fibroglandular elements, 3. heterogeneously dense, or 4. extremely dense. Descriptive analyses were applied. Results: A total of 401 women older than seventy years were diagnosed with breast cancer at our institution. A cohort of 20 (5%) had mammographically occult disease. The median age was 77 years (range 71 to 89 yrs). Of the 20 mammographically occult cases, the majority (75%) were detected as a palpable mass, one was detected by screening US and four were detected by screening MRI. The majority of the cohort (65%) had been screened regularly with mammography prior to diagnosis. When we examined mammographic density, 60% had heterogeneously dense or extremely dense tissue. Nineteen out of twenty were diagnosed with early stage disease. There were 4 cases of DCIS, 10 (50%) were stage 1, and 5 (25%) were stage 2. Seven (35%) had invasive lobular carcinoma on final histopathology. Nine (45%) patients also had an antecedent history of breast cancer; 4 had ipsilateral recurrences and 5 had contralateral new primaries. Only 4 (20%) had a history of HRT use and 7 (35%) had a family history of breast cancer. Discussion: A meaningful proportion of women older than age seventy diagnosed with breast cancer at our institution had mammographicallyoccult disease. A majority (60%) of these patients had heterogeneously dense or extremely dense breast tissue, potentially limiting the sensitivity of mammographic screening in this cohort. In previous work, we evaluated a large number of screening mammograms and reported an incidence of 37% dense breast tissue in women of the same age group. This suggests that increased mammographic density, even in older women, may increase the potential for mammographically occult breast cancer. Particularly for women with increased risk based on a personal or family history of breast cancer, the addition of other imaging modalities may be of value in the presence of mammographically dense tissue regardless of patient age. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P2-01-02.