A better understanding of seasonal variations in cancer diagnosis may be the first step toward optimal resource distribution in the National Cancer Screening Program (NCSP). This study aimed to identify seasonal variations in the diagnosis of the top 10 major cancers in Korea.
We conducted a retrospective, observational cohort study in participants aged ≥ 20 years between 2012 and 2016 from the Health Insurance Review and Assessment-National Patient Sample database, previously converted to a common data model. We assessed the overall seasonal variations in the 10 major cancers.
We analyzed the following top 10 cancers: stomach (n = 3435), colorectal (n = 5368), liver (n = 7605), pancreatic (n = 2946), gallbladder (n = 899), lung (n = 1598), prostate (n = 2897), thyroid (n = 1966), breast (n = 1313), and kidney (n = 668) cancers. All cancers showed similar seasonal variations in diagnosis, with a significant winter peak. A winter peak in diagnosis was observed for NCSP-covered cancers, such as stomach, colon, liver, and breast cancers, as well as other cancers not covered by the NCSP. The winter peak for cancer diagnosis was the highest for breast cancer (74.4%) followed by thyroid (51.0%) and stomach cancers, whereas it was the lowest for pancreatic cancer followed by prostate and colorectal cancers.
Significant seasonal variations were found in the diagnosis of the top 10 major cancers, with a winter peak, which may be explained by the participants’ behavior pattern with respect to the NCSP. Our findings suggest that trading off of NCSP health-care resources between winter and other seasons may be beneficial.

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