Influenza Among Breast Cancer Survivors in South Korea: A Nationwide Population-Based Study

Background/Aim: In this study, we analyzed the prevalence of influenza disease in breast cancer survivors using claims data from the Health Insurance Review and Assessment Service (HIRA) in South Korea. Patients and Methods: We defined influenza among a nationwide cohort of 87,843 patients who were diagnosed with breast cancer and underwent surgery from January 1, 2010 to December 31, 2014, based on HIRA claim data. Descriptive statistics were calculated to estimate the frequency of influenza disease using diagnostic code and utilization pattern at medical institutions. Results: Two thousand four hundred breast cancer survivors (2.7%) were diagnosed with influenza. The overall frequency of influenza increased from November (n=98) and peaked in February (n=1,745). Over 60% (2,693) of claims for influenza disease treatment were in the clinic, whereas general hospitals accounted for 22.0% (873). Among 3,967 claims, admission rate was 7.6% (n= 301) and the average length of hospitalization was 4.7 days. Elderly breast cancer survivors over 70 years old had the longest length of hospitalization at 5.9 days. Conclusion: Breast cancer survivors are more susceptible to influenza than non-cancer survivors. It is important not only to raise the vaccination rate among young cancer survivors, but also to quickly identify symptoms and begin treatment for flu in elderly cancer survivors.