Increasingly strong reduction in breast cancer mortality due to screening.

BACKGROUND: Favourable outcomes of breast cancer screening trials in the 1970s and 1980s resulted in the launch of population-based service screening programmes in many Western countries. We investigated whether improvements in mammography and treatment modalities have had an influence on the effectiveness of breast cancer screening from 1975 to 2008. METHODS: In Nijmegen, the Netherlands, 55,529 women received an invitation for screening between 1975 and 2008. We designed a case-referent study to evaluate the impact of mammographic screening on breast cancer mortality over time from 1975 to 2008. A total number of 282 breast cancer deaths were identified, and 1410 referents aged 50-69 were sampled from the population invited for screening. We estimated the effectiveness by calculating the odds ratio (OR) indicating the breast cancer death rate for screened vs unscreened women. RESULTS: The breast cancer death rate in the screened group over the complete period was 35% lower than in the unscreened group (OR=0.65; 95% CI=0.49-0.87). Analysis by calendar year showed an increasing effectiveness from a 28% reduction in breast cancer mortality in the period 1975-1991 (OR=0.72; 95% CI=0.47-1.09) to 65% in the period 1992-2008 (OR=0.35; 95% CI=0.19-0.64). CONCLUSION: Our results show an increasingly strong reduction in breast cancer mortality over time because of mammographic screening.

Large increase in a Dutch woman's lifetime risk of developing breast cancer.

A large increase in the incidence of breast cancer has been observed in many countries over the last two decades. On the other hand, however, breast cancer mortality has decreased. The prominent burden of breast cancer in the female population induces a lot of discussion about incidence and mortality rates, whereas lifetime risks are less mentioned. This study provides information on the changes in risks for Dutch women with regards to being diagnosed with breast cancer (both invasive and in situ) or dying from this disease during the screening era. We used the life table method to calculate lifetime risks for the period 1989-2003. The lifetime risk for developing breast cancer increased from 1 in 10 in 1989 to 1 in 7 in 2003; the risk of dying from breast cancer decreased respectively from 1 in 22 to 1 in 26. The increasing incidence is alarming but has to be seen in perspective; the decreasing mortality is promising and shows that, at most, one third of the breast cancer cases are fatal.