An analysis of deaths following diagnosis of invasive breast cancer has found that the majority of deaths occur in the minority of women who are not regularly screened, and that half the deaths were women under age 50, according to a study published online Sept. 9 in CANCER.
The results suggest the best method to avoid death from breast cancer is to receive regular screening, even for women ages 40 – 49 in whom screening has been controversial, explained Blake Cady, MD, of Harvard Medical School in Boston, and colleagues.
“In the presence of conflicting evidence, national recommendations for screening mammography have become a point of contention,” wrote the authors. “Surgical procedures, systemic adjuvant therapies and radiation treatments for breast cancer have changed over recent decades, and as breast cancer mortality continues to decline, it is important to determine the proportional decrease in mortality, if any, that is due to modern mammography.”
In 2009, the U.S. Preventive Services Task Force recommended limiting screening to women aged 50 to 74 years. A major concern was overdiagnosis and its associated costs and harms. One potential issue with previous studies, however, is that research into the effects of mammography screening are often based on randomized trials that look forward at outcomes after screening.
The study by Cady and colleagues, on the other hand, was a “failure analysis” that looked backwards from death in individual cases to make correlations with diagnosis and screening. Included in the study were cases of invasive breast cancers diagnosed at Partners HealthCare hospitals in Boston between 1990 and 1999, with follow-up through 2007.
Study co-author Daniel Kopans, MD, of Harvard Medical School and Massachusetts General Hospital, said in a press release that by looking at individual women rather than overall registry data helps avoid false conclusions. “This present paper examines each woman as an individual with direct data on who was screened and which women died of breast cancer. It addresses the question from a different and unique perspective," he said.
A total of 609 confirmed breast cancer deaths were included in the analysis, 29 percent among women who had been screened and 71 percent among unscreened women, reported the authors. Median age at diagnosis for those who died was 49 years, with 50 percent of deaths occurring in women under 50. Only 13 percent of deaths from breast cancer occurred in women aged 70 or older.
“The biological nature of breast cancer in young women is more aggressive, while breast cancer in older women tends to be more indolent,” said Cady. “This suggests that less frequent screening in older women, but more frequent screening in younger women, may be more biologically based, practical and cost effective.”
Aside from emphasizing the role of screening in younger women, the results demonstrated a dramatic shift in breast cancer survival in the screening era. Half of the women diagnosed with breast cancer in 1969 had died within 12.5 years, while just 9.3 percent of the women diagnosed in the present study had died.
In a joint statement, the American College of Radiology and Society of Breast Imaging said the study confirms the need for greater use of annual mammography in women younger than 50, as has been suggested by the American Cancer Society and others.
“These findings should quiet those who argue that women age 40-49 do not need regular mammography screening,” said Barbara S. Monsees, MD, chair of the American College of Radiology Breast Imaging Commission, in the statement. “In fact, these women need annual screening--as do all women 40 and older. This is the message physicians should be promoting.”