ASCO Breast: Most Deaths Fall Outside Screening Programs

SAN FRANCISCO (MedPage Today) -- Nearly three-quarters of breast cancer deaths occur among women who don't get regular screening mammograms, according to a large population-based study.

Breast cancer mortality rates extrapolated from the findings were just 4.7% for women on the recommended screening schedule, but 56% for those who never or only infrequently got mammograms, Blake Cady, MD, of the Cambridge (Mass.) Hospital Breast Center, and colleagues found.

For the latter group, "that is the same as the overall mortality in breast cancer we used to see up until the 1970s, prior to the onset of widespread mammographic screening," Cady reported at the ASCO Breast Cancer Symposium.

These findings provide another line of evidence supporting the efficacy of screening, commented Lori Pierce, MD, of the University of Michigan in Ann Arbor, who moderated a press briefing highlighting these results and served as co-chair of the conference program committee.

"Clearly we have randomized trials of mammography that have shown us that mammograms save lives," she said. This study used a different methodology with "results clearly supporting the finding of the trials, that we must encourage our patients to undergo routine mammographic screening."

Those previous trials, while showing 25% to 40% reductions in breast cancer mortality for women assigned to be offered screening, might have underestimated the benefits, Cady said, since women often didn't follow-through or accept their assignment.

One retrospective study of women who actually received screening has shown a mortality reduction of more than 50%, he noted.

So his group sought to confirm this by following outcomes for 6,997 invasive breast cancers diagnosed in Massachusetts in a large hospital consortium between 1990 and 1999.

After an average of 12.5 years of follow-up, 461 of the women had died from their breast cancer as documented by actual review of hospital and outpatient records.

Among those who died, 74.8% had not had regular screening -- defined as two or more screening mammograms at intervals of two years or less while asymptomatic. For 69.9%, their cancers were picked up when palpable without any prior mammogram.

Another 1.5% had a non-palpable cancer found on their first-ever mammogram and 3.5% had a palpable cancer found after going more than the recommended two years between mammograms.

The 25.2% of deaths among women with regular screening were divided between palpable cancers that appeared in the interval between scheduled mammograms (9.5%) or nonpalpable cancers found on regular mammograms (15.6%).

At every age group up through the 70s, breast cancer deaths occurred predominantly in women who didn't get regular mammograms.

"So even among women in their 50s and 60s who are ideal candidates to be screened, there are many women who are not getting screened and really we should put lots of effort into trying to get them screened," Cady said.

He cautioned that some women in the "unscreened" group may have had legitimate reasons for foregoing regular mammography, such as illness, but poor socioeconomic status, a primary language other than English, or lack of contact with the medical system likely played a part for many.

"The most effective method for women to avoid death from breast cancer is to have regular mammographic screening," Cady concluded.

The researchers reported no conflicts of interest.

Pierce reported having received research funding from the National Institutes of Health and the Breast Cancer Research Foundation.

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