Staging of Breast Cancer and Survival Rates-Reply

In Reply.—  We are grateful to Drs Sutherland and Mather for their comments on our use of relative survival to measure the effectiveness of primary therapy for breast cancer. As they point out, the approximate parallelism (when displayed on a logarithmic scale) of the survival curve beyond a given time implies that the future mortality risk for the patients who survive at least that long is substantially the same as that for comparable members of the population. In this sense, it is proper to say that these breast cancer survivors no longer have mortality risk related to their diagnosis and that, for these patients, therapy has achieved all of the survival benefit that there was reason to hope for. The fraction of patients falling into this category is, thus, a highly plausible measure of the effectiveness of therapy.As in any comparison not based on random allocation to treatment, questions