NEW YORK (Reuters Health) – New research indicates that while mammographic breast density decreases with age, there remains a substantial proportion of older women with dense breasts — a finding that could have important implications for breast cancer screening.

The results show that even for women in their 70s, roughly a third will have dense breasts.

The findings were presented at the 10th annual meeting of the American Society of Breast Surgeons in San Diego, California.

Prior research has linked dense breasts to a 4- to 6-fold increased risk of developing breast cancer, compared to women with less dense breasts. Moreover, dense breasts may impair the sensitivity of screening mammography. Younger age is a well-known correlate of dense breasts, whereas the percentage of postmenopausal and elderly women with this finding was unknown.

To investigate, Dr. Freya Schnabel and colleagues, from the NYU Cancer Institute in New York (part of NYU Langone Medical Center), analyzed data from 500 consecutive patients who underwent yearly screening mammography and were entered in the NYU institutional radiology database. Overall, 4% of women were under 40 years of age, 27% were 40 to 49 years, 30% were 50 to 59 years, 24% were 60 to 69 years, 9% were 70 to 79 years, and 6% were 80 years and older.

The BI-RADS classification system was used to categorize mammographic breast density as almost entirely fatty, scattered fibroglandular tissue, heterogeneously dense, and extremely dense.

As expected, breast density was highest in younger women. Among women in their 40s, for instance, 74% had heterogeneously or extremely dense breasts.

Nonetheless, dense breasts were still common among older women. Heterogeneously or extremely dense breasts were seen in 54%, 42%, and 31% or women in their 50s, 60s, and 70s, respectively.

“Since there are significant outliers at both extremes of age, a woman’s mammographic density should not be assumed, but rather individually assessed,” Dr. Schnabel told Reuters Health. “This is particularly important for high-risk women, who may benefit from an intensive surveillance approach.”

She added, “Our data would suggest that mammographic density, in conjunction with age and overall breast cancer risk assessment, should be considered when assessing the potential benefit of other imaging studies in addition to yearly mammography.”