Mammography screening may be less accurate in breast cancer patients to detect second cancer

Findings support annual mammography screening recommendations but also highlight need for further evaluation in specific groups of women with personal history of breast cancer. Mammography screening in women with a personal history of breast cancer detects second breast cancers at an early stage, but has lower accuracy, compared to screening in women without prior breast cancer, according to a study in the February 23 issue of JAMA.

According to study authors, the high prevalence of breast cancer survivors is due to general gains in life expectancy and to improved survival in women with a personal history of breast cancer, attributable to improvements in local and systemic treatments and early detection. Women with personal history of breast cancer are at risk of developing second breast cancers and are recommended for annual screening mammography, but few high-quality data exist on screening accuracy, according to background information in the article. The authors add that valid estimates of the accuracy of screening mammography are needed to guide clinical practice and policy and to inform clinicians and women with personal history of breast cancer of expected screening outcomes.

Nehmat Houssami, MBBS, PhD, of the University of Sydney, Australia, and colleagues from the Breast Cancer Surveillance Consortium and Group Health Research Institute, Seattle, conducted a study to examine the accuracy and outcomes of screening mammography and factors associated with screening outcomes in women with a personal history of breast cancer, who were matched to women with no prior breast cancer and screened (1996-2007) through facilities affiliated with the Breast Cancer Surveillance Consortium. There were 58,870 screening mammograms in 19,078 women with a history of early-stage (in situ or stage I-II invasive) breast cancer and 58,870 matched (breast density, age group, mammography year, and registry) screening mammograms in 55,315 women with non prior breast cancer.

Women with personal history of breast cancer had 655 second cancers (499 invasive, 156 ductal carcinoma in situ) and women without personal history of breast cancer had 342 cancers (285 invasive, 57 ductal carcinoma in situ) within 1 year of screening mammography. Cancer rates were 10.5 per 1,000 screens in women with personal history of breast cancer, compared to 5.8 per 1,000 screens in women with no prior breast cancer. Cancer rates, cancer detection rate, and number of false-negative results among 1,000 mammograms were 1.3 to 2.6 times higher for women with personal history of breast cancer screens compared with matched screens.

Screening sensitivity in women with personal history of breast cancer was lower (65.4%) compared with that in women with no prior diagnosis of breast cancer screens (76.5%), due largely to lower sensitivity for detection of invasive cancer in women with personal history of breast cancer (61.1%) relative to that in the matched group (75.7%). Sensitivity of screens in women with personal history of breast cancer was similar for detection of ipsilateral and contralateral cancer; and sensitivity for detection of second cancers was higher in women whose first cancer was ductal carcinoma in situ than in those whose first cancer was invasive. Sensitivity in the initial 5 years from first cancer was lower than sensitivity after 5 years. Screen-detected and interval cancers in women with and without personal history of breast cancer were predominantly early stage.

Despite a relatively high interval cancer rate, interval cancers in women with personal history of breast cancer had generally favourable stage distributions. The screening outcomes and breast cancer rates in women with personal history of breast cancer are associated with various factors, including the treatment received for the first cancer, so these women have heterogeneous underlying risks for a second breast cancer, and a more tailored screening strategy than currently recommended might be warranted, the author wrote.

The researchers concluded that their findings support annual mammography screening recommendations in women with personal history of breast cancer but also highlight issues needing further evaluation, such as additional or alternate screening in specific groups of women who had very high rates of interval cancers including women younger than 50 years of age, women with extremely dense breasts, and those who received breast conservation without radiotherapy for their first cancer.

Source: ESMO