HRT and low body mass reduce sensitivity of mammography

Screening mammography is less effective in detecting breast cancer in women who use hormone replacement therapy (HRT). This is also true of those who have undergone breast surgery, or who are thin, UK investigators report in the August 28th issue of the British Medical Journal.

To examine how patients’ personal characteristics affect the accuracy of mammography, Dr. Emily Banks, at Radcliffe Infirmary, Oxford and colleagues examined data on 122,355 women aged 50 to 64 who had undergone breast screening. They had also completed questionnaires on lifestyle and sociodemographic factors, reproductive factors, past health and use of HRT.Results showed that 0.51% had cancer detected at screening, and 0.08% had negative results, but were diagnosed with cancer within the next 12 months. Another 3.2% had false positive results. The authors calculated the sensitivity and specificity according to various characteristics, adjusting for age, screening center, body mass index (BMI), previous breast surgery, menopausal status and use of HRT.Among current HRT users, the adjusted sensitivity of mammography was 83.0% compared with 92.1% for never users. Corresponding specificities were 96.8% and 97.9%. Sensitivity and specificity for past users were still significantly lower than never users (84.75% and 97.6%).Screening results were also affected by history of breast surgery. Sensitivity was 89.4% among those with no prior surgery and 83.5% for those who had had such surgery.For those with a BMI less than 25, the sensitivity was 85.7%, compared with 89.8% for women with higher BMIs.The authors posit that use of HRT, breast surgery and low BMI are associated with increased radiographic density, which in turn reduces accuracy of mammography.Nevertheless, co-author Dr. Gillian Reeves stressed in a statement that regardless of these variations, mammography “remains the best way of detecting breast cancer when it is still at an early stage.”(Source: BMJ 2004;329:477-479: Reuters Health News: August 2004.)