Mammography screening outcomes, gauged in terms of tumor size, lifetime gained, and mortality, have typically been poorer in women in their 40s than women in their 50s, somewhat because tumors of younger women are inclined to grow more quickly, so by the time they grow to a detectable size, they would have probably already been detected by a routine examination. Younger women also tend to have denser breast tissue, which can hide tumors, reducing their detectability on mammograms.

To investigate which aspect--faster tumor growth rates, or reduced mammographic detectability--contributes to poorer mammography screening outcomes in younger women, Dr. Sylvia K. Plevritis, from the department of radiology at the Stanford University School of Medicine (Palo Alto, CA, USA), and colleagues, utilized a computer-simulated model to estimate the relative effect of biology and technology on mammograms of women in their 40s, compared to women in their 50s and 60s.

The researchers utilized the Breast Cancer Screening Simulator to create hypothetic screening situations whereby they could estimate the median tumor size detectable on a mammogram and the mean tumor growth rate in women aged 40-49 and 50-69. The researchers concluded from their simulation model that lowered mammographic tumor detectability accounted for 79% and faster tumor volume doubling time accounted for 21% of the poorer sensitivity in mammography screening among younger women, compared with older women.

The study's findings were published online July 27, 2010, in the Journal of the [U.S.] National Cancer Institute. The authors wrote, "The age-specific differences in mammographic tumor detection contribute more than age-specific differences in tumor growth rates to the lowered performance of mammography screening in younger women.”

One limitation of the analysis, according to the investigators, is that it did not take into account that low mammographic tumor detectability could be considered a breast cancer risk factor. They reported, "More research is needed to not only establish a better relationship between mammographic breast density and breast cancer risk but also understand the differences in tumor characteristics in dense vs. nondense breast tissue.”

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Stanford University School of Medicine