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Statistical Methods for Survival Data Analysis Third Edition phần 3

đã thông qua ý tưởng Greenwood so sánh các kinh nghiệm sống còn của bệnh nhân ung thư với dân số nói chung để xác định (1) các tỷ lệ quan sát được tỷ lệ sống sót dự kiến và (2) cho dù, trong thời gian, tỷ lệ tử vong từ chối mức độ "bình thường". | RELATIVE FIVE-YEAR AND CORRECTED SURVIVAL RATES 95 random sample of persons of the same age gender occupation and so on the patients could be considered cured. Cutler et al. 1957 1959 1960a b 1967 adopted Greenwood s idea of comparing the survival experience of cancer patients with that of the general population to ascertain 1 the ratio of observed to expected survival rates and 2 whether in time the mortality rate declines to a normal level. The relative survival rate is defined as the ratio of the survival rate probability of surviving one year for a patient under study observed rate to someone in the general population of the same age gender and race expected rate over a specified period of time. To provide a more precise measure of the relationship of the observed and expected survival rates Cutler et al. suggest computing the ratio for each individual follow-up year. A relative rate of 100 means that during a specific follow-up year the mortality rates in the patient and in the general population are equal. A relative rate of less than 100 means that the mortality rate in the patients is higher than that in the general population. Cutler et al. use the survival rates in the Connecticut and U.S. life tables for the general population. Using the notations in Table 4.6 the survival rate observed at time tt is Pl the expected survival rate can be computed as follows Suppose that at time t there are n individuals alive for whom age gender race and time of observation are known. Let p be the survival rate of the j th individual from general population life tables with corresponding age gender and race . The expected survival rate is . 1 M . p 1 Ẽ p 4.3.1 n i J Then the relative survival rate at time t is defined by rt p 4.3.2 Example 4.5 taken from Cutler et al. 1957 illustrates the interpretation of relative survival rates. Example 4.5 A total of 9121 breast cancer cases were diagnosed in Connecticut hospitals from 1935 to 1953. The Connecticut life table for white