Avoidance of premature death: a new definition for the proportion cured.

For many cancers, five-year survival is used as a synonym for cure. For some sites, such as breast, this is inappropriate since there is still considerable excess mortality 5-15 years following diagnosis. We propose using the probability of not dying prematurely as a surrogate for the probability of being cured. This is estimated without the need for information on the cause of death by comparing all-cause-mortality rates in patients with cancer to those in the general population. We also consider the probability of 'cure' in those who have survived a certain number of years since diagnosis. These quantities are estimated for various cancer sites using SEER data. The proportion not dying prematurely varies considerably for common cancers from 12% for lung cancer to 84% for prostate cancer. In women, the percentage 'cured' for colon and breast cancer are very similar at 56% and 58% respectively, but in those who survive 5 years, they are quite different--91% and 78% respectively. The proposed statistic is useful. For diseases in which excess mortality is primarily within five years of diagnosis, it agrees well with 5-year relative survival. Interpretation of differences between countries or over time is complicated and requires consideration of incidence and mortality data.