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Background: The proportion of cases notified by death certificate only (DCO) is a commonly used data quality indicator in studies comparing cancer survival across regions and over time. We aimed to assess dependence of DCO proportions on the age structure of cancer patients. Methods: Using data from a national cancer survival study in Germany, we determined age specific and overall (crude) DCO proportions for 24 common forms of cancer. We then derived overall (crude) DCO proportions expected in case of shifts of the age distribution of the cancer populations by 5 and 10 years, respectively, assuming age specific DCO proportions to remain constant. Results: Median DCO proportions across the 24 cancers were 2.4, 3.7, 5.5, 8.5 and 23.9% in age groups 15-44, 45-54, 55-64, 65-74, and 75+, respectively. A decrease of ages by 5 and 10 years resulted in decreases of cancer specific crude DCO proportions ranging from 0.4 to 4.8 and from 0.7 to 8.6 percent units, respectively. Conversely, an increase of ages by 5 and 10 years led to increases of cancer specific crude DCO proportions ranging from 0.8 to 4.8 and from 1.8 to 9.6 percent units, respectively. These changes were of similar magnitude (but in opposite direction) as changes in crude 5-year relative survival resulting from the same shifts in age distribution. Conclusions: The age structure of cancer patient populations has a substantial impact on DCO proportions. DCO proportions should therefore be age adjusted in comparative studies on cancer survival across regions and over time. [ABSTRACT FROM AUTHOR]

Background: Previous population-based studies revealed major variation in survival for patients with colorectal cancer (CRC) in Europe by age and between different countries and regions, but also a sustained improvement in survival for patients with CRC in recent years. This EUROCARE-5 paper aims to update available knowledge from previous studies and to provide the latest survival estimates for CRC patients from Europe. Methods: The study analysed data of patients diagnosed with CRC from population-based cancer registries diagnosed in 29 European countries. Estimates of 1-year and 5-year relative survival (RS) were derived for patients diagnosed in 2000-2007 by European region, country and age at diagnosis. Additionally to these cohort estimates, time trends in 5-year RS were obtained for the calendar periods 1999-2001 and 2005-2007, using the period analysis methodology. Results: European average 5-year RS for patients diagnosed with colon and rectum cancer was 57% and 56%, respectively. The analyses showed persistent differences in cancer survival across Europe with lowest survival for CRC patients observed in Eastern Europe. The analyses further showed a strong gradient in age-specific survival. Even though the study revealed sustained improvement in patient survival between 1999-2001 and 2005-2007 (absolute increase of 4 and 6 percentage points for colon and rectum, respectively), the differences in the survival for CRC patients observed at the beginning of the millennium persisted over time. Conclusion: Although survival for CRC patients in Europe improved markedly in the study period, significant geographic variations and a strong age gradient still persisted. Enhanced access to effective diagnostic procedures and treatment options might be the keys to reducing the existing disparities in the survival of CRC patients across Europe. [ABSTRACT FROM AUTHOR]