1. After implementation of routine screening in older women, the incidence of early stage breast cancer increased, but there was only a minimal absolute decrease in the incidence of advanced stage breast cancer.
2. For each advanced staged tumor that was detected approximately 20 extra, early stage tumors were detected.
3. Based on the minimal decrease in the incidence of advanced stage cancers over program implementation, the authors suggest that screening is of limited value in patients over 75 and may lead to overdiagnosis and unnecessary testing.
Evidence Rating Level: 1 (Excellent)
Study Rundown: Generally, breast screening programs aim to decrease the incidence of advanced stage cancers. Several guidelines recommend breast cancer screening in women up to age 75, however there is no clear evidence supporting the benefits of screening for breast cancer in older women. Trial data for breast cancer screening primarily included women age 60 or younger. In the Netherlands, breast cancer screening was extended to women aged 70-75 in 1998. This prospective study sought to determine the effect of screening older women on the incidence of early and advanced stage breast cancer. The incidence of each type of cancer before and after implementation of routine screening in older women was assessed. After extension of the upper age of routine screening to 75 years, there was a large increase in the incidence of early stage tumors, but the incidence of advanced stage breast cancer decreased minimally.
The data for this study were well documented and detailed, as they were derived from a national cancer registry in the Netherlands. Analysis of the dataset allowed for evaluation of change in breast cancer incidence over time. Further, the availability and attendance rate of routine preventive health care in the Netherlands is high, enhancing the reliability of the study’s results. However, this analysis had a limited follow-up time, thus it is possible that insufficient time had passed to detect a decrease in the incidence of advanced stage tumors. Overall, these data provide evidence that extending breast cancer screening to older women does not decrease incidence of advanced stage cancer, suggesting that routine screening in older women is of limited effect.
In-Depth [prospective cohort]: This study evaluated the effect of extending the age for routine breast cancer screening to 75 years in the Netherlands, by evaluating and comparing the incidence of early stage and advanced stage breast cancer before and after implementation of extended upper age limits for screening. Incidence rates were calculated using population data from a national cancer registry, divided into a period before screening (1995-97), during screening uptake (1998-2002), and a period after implementation (2003-11). Changes in incidence rate ratios were analyzed using Poisson regression. The incidence of early stage breast cancer significantly increased after extension of the upper age limit in 1998, from 248.7 cases per 100,000 women to 362.9 cases per 100,000 women (incidence rate ratio 1.46 [CI95% 1.40-1.52]). While a statistically significant decrease in advanced stage tumors was found, the absolute decrease was minimal, from 58.6 cases per 100,000 women prior to screening to 51.8 cases per 100,000 women after implementation of the extended age limit (incidence rate ratio 0.88 [CI95% 0.81-0.97]). The ratio of the incidence of advanced stage tumors to the incidence of early stage tumors was 19.7 cases per 100,000 women per year, indicating that for each advanced stage tumor prevented by screening, 19.7 “extra” early stage tumors were detected.
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