9.6 Recent trends in breast cancer mortality

During the period 1950–1960, the annual mortality rate for breast cancer in the age-range 35–69 years, calculated as the mean of the seven age-specific rates 35–39, 40–44, ... , 65–69 in the United Kingdom was around 58 per 100,000 women; see the left part of Figure 9.1. From about 1960, the rate started to rise, as in many other European countries, and this rise continued steadily until the late 1980s, by which time it was over 70 per 100,000 women. In 1990, however, it suddenly started to fall and it has fallen continuously since then, so that in 2000 it was only just over 50 deaths per 100,000, well below its value in the 1950s.

During the 1990s, lesser decreases have also occurred in several other countries, including the United States (Peto et al. 2000); see the right part of Figure 9.1. Recent data on breast cancer incidence, as opposed to mortality, are difficult to interpret as they are affected by screening. For example, in the UK the national screening program was introduced in 1987 for women aged 50–64, and has undoubtedly resulted in many cancers in this age range being diagnosed earlier than they would otherwise have been. However, there is no suggestion from the incidence rates at ages below 50 or above 65 of a sudden decrease in the underlying trend of breast cancer incidence rates that might be responsible for the recent decrease in mortality (Quinn et al. 2001). Some of the downward trends in mortality are likely to be the effect of the screening program, and detailed analyses have estimated that in the UK screening is responsible for 30–40% of the fall in mortality in age-groups 55–69 (Blanks et al. 2000, Sasieni 2003). The remaining 60–70% is likely to be explained partly by the tendency towards earlier presentation outside the screening program, but mostly by the increasing use of tamoxifen and chemotherapy from the mid-1980s, which has been helped by the EBCTCG analyses. In 2000, a United States National Institutes of Health Consensus Statement on adjuvant therapy for breast cancer (National Institutes of Health 2000) drew heavily on the findings of the EBCTCG for their recommendations on the use of tamoxifen, ovarian ablation and polychemotherapy. As a result of this and of similar treatment guidelines in other countries, further falls in breast cancer mortality worldwide can be expected in the future. At the same time new treatments for breast cancer that require rigorous assessment continue to be developed and provide further questions for assessment in future cycles of the EBCTCG.

Since this chapter was written, the report on the effects of chemotherapy and hormonal therapy of the fourth cycle of the EBCTCG has been published (EBCTCG, 2005). This shows that some of the widely practicable adjuvant drug treatments that were being tested in the 1980s, which substantially reduced 5-year recurrence rates, also substantially reduce 15-year mortality rates. In particular, for middle-aged women with ER-positive disease, the breast cancer mortality rate throughout the next 15 years would be approximately halved by 6 months of anthracycline-based chemotherapy followed by 5 years of adjuvant tamoxifen. For, if mortality reductions of 38% (age < 50 years) and 20% (age 50–69 years) from such chemotherapy were followed by a further reduction of 31% from tamoxifen in the risks that remain, the final mortality reductions would be 57% and 45%, respectively. Overall survival would be comparably improved, since these treatments have relatively small effects on mortality from the aggregate of all other causes. Further improvements in long-term survival could well be available from newer drugs, or better use of older drugs.