Background: Recent improvements in 5-year survival of breast cancer have been reported in Japan and other countries. Though the number of long-term breast cancer survivors has been increasing, recent improvements in 10-year survival have not been reported. Moreover, the degree of improvement according to age and disease stage remains unclear.
Methods: We calculated long-term survival using data on breast cancer diagnosed from 1993 through 2006 from six prefectural population-based cancer registries in Japan. The recent increase in 10-year relative survival was assessed by comparing the results of period analysis in 2002-2006 with the results of cohort analysis in 1993-1997. We also conducted stratified analyses by age group (15-34, 35-49, 50-69, and 70-99 years) and disease stage (localized, regional, and distant).
Results: A total of 63,348 patients were analysed. Ten-year relative survival improved by 2.4% (76.9% vs 79.3%) from 1993 through 2006. By age and stage, 10-year relative survival clearly improved in the age 35-49 years (+2.9%; 78.1% vs 81.0%), 50-69 years (+2.8%; 75.2% vs 78.0%) and regional disease (+3.4%; 64.9% vs 68.3%). In contrast, the degree of improvement was small in the age 15-34 years (+0.1%; 68.2% vs 68.3%), 70-99 years (+1.0%; 87.6% vs 88.6%), localized disease (+1.1%; 92.6% vs 93.7%) and distant metastasis (+0.9%; 13.8% vs 14.7%).
Conclusions: These population-based cancer registry data show that 10-year relative survival improved 2.4% over this period in Japan. By age and stage, improvement in the age 15-34 years and distant metastasis was very small, which suggests the need for new therapeutic strategies in these patients.
Keywords: breast cancer; cancer registration; long-term survival; period analysis; relative survival.