March 22, 2012 — Even in the era of improved adjuvant therapy, population-based screening programs significantly reduce breast-cancer-related mortality.
In a study presented at the 8th European Breast Cancer Conference (EBCC-8), held in Vienna, Austria, Dutch researchers found that biennial screening in women 50 years and older reduced mortality by 15.7%. Using a computerized model, they found that adjuvant systemic therapy reduced breast cancer mortality by 13.7%; lowering the age limit for screening resulted in an additional, albeit slight, reduction in mortality.
"The Netherlands has a breast cancer screening program that invites women between the ages of 50 and 75 years for screening," said study author Rianne de Gelder, a PhD student and researcher at the Erasmus University Medical Center in Rotterdam, the Netherlands. "We have found it to be very effective."
There has been much debate about the ability of screening mammography to reduce mortality and whether it does more harm than good, explained de Gelder, who presented the highlights of the research during a press briefing. Some research shows that population-based mammography programs can save a significant number of lives; other research shows that mortality reductions are largely related to the use of adjuvant therapy.
We wondered which was true, said de Gelder. Does breast cancer screening reduce "breast cancer mortality or is adjuvant therapy so effective nowadays that its effects are as large as screening?"
de Gelder and colleagues looked at another question: What are the additional effects of screening before age 50? In the Netherlands, screening begins at age 50, as it does many other European countries.
"We are seeing an increasing incidence of breast cancer in women younger than 50, so we wanted to see what the effect would be," she explained, adding that the additional effect of mammography screening when an increasing number of patients are receiving adjuvant treatment is unclear, particularly for those 40 to 49 years of age.
Microsimulation Model Shows Screening Reduces Mortality
The researchers used a microsimulation model to assess the effects of adjuvant therapy, biennial screening from ages 50 to 74 (the current screening age range) in the presence of adjuvant therapy, and lowering the screening age from 50 to 40 years. Breast cancer mortality was compared in scenarios with and without these interventions.
The microsimulation model used both Dutch and international statistics on breast cancer incidence, survival, mortality, and screening programs. The model also incorporated data on the use and effectiveness of adjuvant breast cancer treatments.
Dutch mortality data from 1975 to 2008 were used in the model to determine breast cancer mortality; thus, data were included from a time period when screening was not an option and adjuvant therapy was rarely used.
The researchers found that adjuvant treatment reduced breast cancer mortality from 67.4 to 57.9 per 100,000 women-years. With the addition of biennial screenings for women 50 to 75 years, the death rate declined to 48.8 per 100,000 women-years, indicating that adjuvant therapy combined with screening reduced deaths by 27.4%
"If we added 10 more screening rounds, starting at age 40, we see an additional reduction in breast cancer mortality of 5.1%," said de Gelder. "One additional screening round would further reduce breast cancer mortality at age 48 by 1%."
However, she added that the observed reduction in breast cancer mortality cannot be fully explained by mammography screening and adjuvant therapy; other factors most likely contribute to these rates.
"This study will make an important contribution to the ongoing debate about the level of benefit of a population-based mammographic screening program," said David Cameron, MD, MRCP, professor of oncology at the University of Edinburgh, United Kingdom, and chair of the EBCC-8, in a statement. "Many aspects of breast cancer management have improved since the original randomized trials of breast cancer screening, so it is important to dissect out the relative contributions of treatment, screening, and other changes in management."
8th European Breast Cancer Conference (EBCC-8): Abstract 28. Presented March 21, 2012.
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