For women with a history of breast cancer, mammography can detect a second cancer at an early stage, but is less accurate than screenings on women who've never had the disease, according to new research.

Screenings of women with a personal history of breast cancer (PHBC) were nearly 12 percentage points less sensitive than were screenings for non-PHBC women, largely because of poorer sensitivity for invasive cancers, according to the study, which appears in the February 23 issue of the Journal of the American Medical Association.

"In general, screening did not perform as well in PHBC women relative to that in women without PHBC," wrote the researchers, led by Nehmat Houssami, of the University of Sydney, Australia. "Sensitivity and specificity were lower for PHBC women, and screening examinations were approximately twice as likely to be recommended for additional imaging or biopsy."
In the study, the researchers evaluated 58,870 screening mammograms in 19,078 women with a history of early-stage breast cancer and 58,870 matched (breast density, age group, mammography year, and registry) screening mammograms in 55,315 non-PHBC women. These women were screened from 1996 to 2007 at facilities affiliated with the Breast Cancer Surveillance Consortium Group Health Research Institute in Seattle.

The researchers found that sensitivity in PHBC was 65 percent, compared with 77 percent sensitivity for non-PHBC screens. This was largely due to lower sensitivity (61 percent) for invasive cancer compared with the matched group (76 percent), the researchers said.

Sensitivity of screens for women with a history of breast cancer was similar for treated and untreated breasts. It was also lower in the first five years following discovery of the first cancer. For these women, sensitivity was also higher if the original cancer was ductal carcinoma in situ than if it had been invasive.

Women with PHBC had 655 second cancers, and women without PHBC had 342 cancers within 1 year of screening mammography. Cancer rates were 10.5 per 1,000 screens in PHBC women, compared to 5.8 per 1,000 screens in non-PHBC women. Cancer rates, cancer detection rate and interval cancer rate (number of false-negative results among 1,000 mammograms) were 1.3 to 2.6 times higher for PHBC screens compared with matched screens.

"As we know, women with a personal history of breast cancer are at a higher risk of developing a second breast cancer than the general public," said Dr. Pamela Otto, director of the breast imaging center at the Cancer Therapy & Research Center at the University of Texas Health Science Center in San Antonio. "This being said, it is not surprising that the cancer rates and cancer detection rates were higher in women with personal history of breast cancer than those with no personal history."

Houssami and fellow researchers concluded that their findings support annual mammography screening recommendations in PHBC women but also highlight issues needing further evaluation, such as additional screening in specific groups of PHBC women who had very high rates of interval cancers, including women younger than 50 and those with extremely dense breasts.

"I agree that we probably need to better screen these women by possibly adding ultrasound or MRI," Otto said. She said the American Cancer Society has guidelines that address MRI screening for PHBC patients.

"Those with dense breasts who have a personal risk of developing breast cancer in the 15-20 percent range should be considered for screening MRI of the breast," she said, citing the guidelines.

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