A useful summary measure for survival data is the expectation of life, which is calculated by obtaining the area under a survival curve. The loss in expectation of life due to a certain type of cancer is the difference between the expectation of life in the general population and the expectation of life among the cancer patients. This measure is used little in practice as its estimation generally requires extrapolation of both the expected and observed survival. A parametric distribution can be used for extrapolation of the observed survival, but it is difficult to find a distribution that captures the underlying shape of the survival function after the end of follow-up. In this paper, we base our extrapolation on relative survival, because it is more stable and reliable. Relative survival is defined as the observed survival divided by the expected survival, and the mortality analogue is excess mortality. Approaches have been suggested for extrapolation of relative survival within life-table data, by assuming that the excess mortality has reached zero (statistical cure) or has stabilized to a constant. We propose the use of flexible parametric survival models for relative survival, which enables estimating the loss in expectation of life on individual level data by making these assumptions or by extrapolating the estimated linear trend at the end of follow-up. We have evaluated the extrapolation from this model using data on four types of cancer, and the results agree well with observed data.
Purpose Chronic myeloid leukemia (CML) management changed dramatically with the development of imatinib mesylate (IM), the first tyrosine kinase inhibitor targeting the BCR-ABL1 oncoprotein. In Sweden, the drug was approved in November 2001. We report relative survival (RS) of patients with CML diagnosed during a 36-year period. Patients and Methods Using data from the population-based Swedish Cancer Registry and population life tables, we estimated RS for all patients diagnosed with CML from 1973 to 2008 (n = 3,173; 1,796 males and 1,377 females; median age, 62 years). Patients were categorized into five age groups and five calendar periods, the last being 2001 to 2008. Information on use of upfront IM was collected from the Swedish CML registry. Results Relative survival improved with each calendar period, with the greatest improvement between 1994-2000 and 2001-2008. Five-year cumulative relative survival ratios (95% Cls) were 0.21 (0.17 to 0.24) for patients diagnosed 1973-1979, 0.54 (0.50 to 0.58) for 1994-2000, and 0.80 (0.75 to 0.83) for 2001-2008. This improvement was confined to patients younger than 79 years of age. Five-year RSRs for patients diagnosed from 2001 to 2008 were 0.91 (95% CI, 0.85 to 0.94) and 0.25 (95% CI, 0.10 to 0.47) for patients younger than 50 and older than 79 years, respectively. Men had inferior outcome. Upfront overall use of IM increased from 40% (2002) to 84% (2006). Only 18% of patients older than 80 years of age received IM as first-line therapy. Conclusion This large population-based study shows a major improvement in outcome of patients with CML up to 79 years of age diagnosed from 2001 to 2008, mainly caused by an increasing use of IM. The elderly still have poorer outcome, partly because of a limited use of IM.
Background Disquieting reports of increased complication and death rates after transfusions of red-cell concentrates stored for more than 14 days prompted us to perform an observational retrospective cohort study of mortality in relation to storage time. Study design and methods We conducted a cohort study utilizing data on all recipients of at least one red-cell transfusion in Sweden and Denmark between 1995 and 2002, as recorded in the Scandinavian donations and Transfusions (SCANDAT) database. Relative risks of death in relation to storage time were estimated using Cox regression, adjusted for several possible confounding factors. Results After various exclusions, 402,874 transfusion episodes remained for analysis. The 7 day risk of death was similar in all exposure groups, but a tendency for a higher risk emerged among recipients of blood stored for 30-42 days (hazard ratio, 1.05; 95% CI, 0.97-1.12), as compared to recipients of blood stored for 10-19 days. With 2-year follow-up, this excess remained at the same level (hazard ratio, 1.05; 95% CI, 1.02-1.08). No dose-response pattern was revealed and no differential effect was seen when the analyses were restricted to recipients of leukocyte depleted units only. Conclusion Although a small excess mortality was noted in recipients of the oldest red-cell concentrates, the risk pattern was more consistent with weak confounding than with an effect of the momentary exposure to stored red-cell concentrates. It seems, thus, that any excess mortality conferred by older red-cells in the combined Swedish and Danish transfusion recipient population is likely less than 5%, which is considerably smaller than in the hitherto largest investigation.
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