Relative survival among cancer survivors enrolled in private cancer insurance in Japan, using the internal insurance-enrolled population as the reference.

BACKGROUND

Limited data are available on relative survival (RS) among cancer survivors enrolled in private cancer insurance in Japan. Additionally, the incidence of second primary cancers or recurrences, as applicable, after a certain period remains unclear.

METHODS

We analyzed 8,846 cancer survivors, including carcinoma in situ, aged 15-79 years, enrolled in private cancer insurance between April 2005 and September 2021, and diagnosed before April 2022. Using the entire insurance-enrolled population as the reference, we estimated sex- and age group-specific RS, conditional RS (CRS), and age-standardized RS (ASR) by cancer type. The cumulative incidence of second primary cancers or recurrences, as applicable, was calculated among cancer-free 3-, 4-, and 5-year survivors.

RESULTS

Median ages at first diagnosis were 61.5 years for males and 55.0 years for females. Over median follow-up of 3.40 years, 1,772 deaths (45.4 per 1,000 person-years) occurred. The 5-year RS declined with age: 81.8% for males and 94.8% for females aged 15-39, but 68.5% and 71.8% for those aged 70-79. The 5-year CRS increased with time since diagnosis, exceeding 90% among 5-year survivors in all groups except males aged 70-79. Liver cancer survivors had the highest incidence of second primary cancers or recurrences, predominantly due to recurrences, even after 5 cancer-free years.

CONCLUSION

We estimated sex- and age group-specific RS, CRS, and ASR by cancer type, and the incidence of second primary cancers or recurrences, using a database of private cancer insurance policyholders, though the findings may not be generalizable to the national population.