Study Confirms Value of Routine Mammograms

SAN FRANCISCO — Only 21% of Massachusetts women older than age 40 years were not in mammographic screening programs. Yet unscreened women accounted for 75% of the breast cancer deaths in an analysis of data on 6,997 invasive breast cancers diagnosed in 1990-1999 and followed through 2007.

“The most effective method for women to avoid death from breast cancer is to have regular mammographic screening,” Dr. Blake Cady said at a breast cancer symposium sponsored by the American Society of Clinical Oncology, where he presented the data.

Extrapolation from the study's results suggests that for the projected 192,370 women nationwide diagnosed with invasive breast cancer in 2009, the overall 12.5-year mortality rate of 15% represents rates of 4.7% among regularly screened women and 56% among unscreened women, according to Dr. Cady, professor of surgery at Brown University in Providence, R.I., and professor of surgery emeritus at Harvard Medical School in Boston.

That 56% mortality rate is “the same overall mortality we used to see in breast cancer up until 1970, prior to the onset of widespread mammographic screening,” Dr. Cady said.

These findings confirm previous studies that found 25%-40% reduced mortality in women who were offered mammographic screening and greater than 50% reduced mortality in women who actually received mammograms, he noted.

The results of the current study “clearly support the findings of the trials—that we must encourage our patients to undergo routine screening mammograms,” Dr. Lori Pierce, professor of radiation oncology at the University of Michigan, Ann Arbor, commented at a press briefing.

Dr. Cady and his associates identified 461 patients who died from breast cancer during a median follow-up of 12.5 years and whose hospital and outpatient medical records were available for review. Women were considered to be in mammographic-screening programs if they'd had two or more screening mammograms at intervals of 2 years or less when asymptomatic.

Data from the 1995 Behavioral Risk Factor Surveillance System suggested that approximately 79% of Massachusetts women aged older than 40 years were in mammographic screening programs in 1995.

Among the 461 breast cancer deaths that occurred during the current study, just 116 (25.2%) were in regularly screened women. These included 72 (15.6%) deaths from nonpalpable cancers detected on screening mammography and 44 (9.6%) from palpable cancers detected during an interval between scheduled mammograms, reported Dr. Cady.

The 345 breast cancer deaths (74.8% of the total) in women who were not regularly screened included 322 (69.8%) in women who had never been screened by mammography and 23 (5%) deaths in women who had received one or more previous mammograms, but not within the 2 years before diagnosis of breast cancer.

“Even in women in their 50s and 60s, who are ideal candidates to be screened, there are many women who are not getting screened,” Dr. Cady said. “We should put lots of effort into trying to get them screened, since that's the best way for them to avoid death from breast cancer.”

The 79% rate of regular mammographic screening in Massachusetts is a relatively high rate, compared with rates in other states, and is second only to that of Rhode Island, he noted.

The reasons for this success are unclear, but could be due to better publicity for screening programs, or greater physician awareness and encouragement of screening, or other factors, Dr. Cady suggested in an interview after his presentation.

The lack of screening could be due to many factors such as other illnesses, older age, poverty, language barriers, a history of cancer, or medical advice not to get mammograms for other health reasons, he noted.

Dr. Cady and Dr. Pierce reported having no conflicts of interest related to the study.