Advanced detection of recent changing trends in gastric cancer survival: up-to-date comparison by period analysis.

OBJECTIVE To establish a comprehensive cancer treatment and prevention policy, data collection should be performed in a timely manner, and survival analysis needs to reflect changes in treatment strategy. Therefore, we introduced the concept of period analysis for gastric cancer, the most prevalent cancer in Korea. We estimated 5- and 10-year survival trend of gastric cancer, based on data from the Yonsei Cancer Center Tumor Registry between 1990 and 2004. METHODS We compared the differences in survival between cohort, complete and period analyses for two different periods, 1995-99 and 2000-04. RESULTS A total of 11 724 cases were included. The median age of cancer diagnosis gradually increased over time, and more patients were diagnosed with Stage I disease in recent years. In the basic comparison of three estimated analytic methods (cohort, complete and period), period analysis (45.8%) was most similar to the actual 5-year observed survival rate (48.5%), when compared with cohort (43.6%) and complete (44.8%) analyses. When we compared survival between different 10-year periods (1990-99 and 1995-2004), period analysis demonstrated a greater difference than complete analysis (9.0 versus 3.9%). Subgroup analysis indicated that the survival improvement was determined by period analysis, and it was more pronounced for the age group <74 years and in Stages III-IV patients. CONCLUSIONS We observed that period analysis demonstrates the most similar results to the actual observed survival and is, therefore, a useful method to derive precise cancer survival in gastric cancer. This information is useful to understand survival differences that are influenced by changing treatment strategy.