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This 20-year single-center study retrospectively analyzed 96,174 patients at the Korea Cancer Center Hospital (2003–2022) and identified 2,167 metachronous MPC cases using SEER criteria. Overall MPC incidence was 2.3%, with breast cancer most common and lung cancer the leading second primary. Median latency for second primaries was 4.1 years, decreasing for later primaries. 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Incidence and Characteristics of Multiple Primary Cancers: A 20-Year Retrospective Study of a Single Cancer Center in Korea. Cancers 2024, 16, 2346. [https://doi.org/10.3390/](https://doi.org/10.3390/)[ ](https://doi.org/10.3390/)cancers16132346  \nAcademic Editor: Stefan Ambs  \nReceived: 26 April 2024  \nRevised: 20 June 2024  \nAccepted: 24 June 2024  \nPublished: 26 June 2024  \nCopyright: © 2024 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ([https://](https://)[ ](https://)[creativecommons.org/licenses/by/](creativecommons.org/licenses/by/)[ ](creativecommons.org/licenses/by/)[4.0/](4.0/)) .  \n1 Medical Science Demonstration Center, Korea Cancer Center Hospital, Korea Institute of Radiological and Medical Sciences, Seoul 01812, Republic of Korea; [peterjane19@kirams.re.kr](peterjane19@kirams.re.kr)  \n2 Department of Laboratory Medicine, Korea Cancer Center Hospital, Korea Institute of Radiological and Medical Sciences, Seoul 01812, Republic of Korea; [jklee@kirams.re.kr](jklee@kirams.re.kr) (J.K.L.); [clinchem@kirams.re.kr](clinchem@kirams.re.kr) (Y.J.H.)  \n3 Division of Hematology-Oncology, Department of Internal Medicine, Korea Cancer Center Hospital, Seoul 01812, Republic of Korea; [hyejin@kirams.re.kr](hyejin@kirams.re.kr) (H.J.K.); [dbswjd0305@kirams.re.kr](dbswjd0305@kirams.re.kr) (Y.J.J.)  \n* [Correspondence: heyjin@kirams.re.kr](Correspondence: heyjin@kirams.re.kr)  \nSimple Summary: The incidence of multiple primary cancers (MPCs) among 96,174 cancer patients at the Korea Cancer Center Hospital (KCCH) from 2003 to 2022 was 2.3% . Breast cancer (15.7%) was the most common primary cancer, with lung cancer (15.2%) being the most frequent second primary cancer. The median latency period for second primary cancers was 4.1 years, decreasing for third and fourth primary cancers (2.1 years and 1.6 years, respectively) . Lymphoma had the highest relative risk (2.1) for developing MPCs. Specific primary cancers showed significant associations with subsequent cancers, informing future research and management strategies.  \nAbstract: Rising cancer survival rates have led to an increased risk of multiple primary cancers (MPCs) . Data on MPCs in South Korea are limited. This study aimed to address incidence and clinical characteristics of MPCs in a single cancer center in Korea during a 20-year period. We retrospectively analyzed 96,174 cancer patients at the Korea Cancer Center Hospital between 2003 and 2022, identifying 2167 patients with metachronous MPCs based on Surveillance, Epidemiology, and End Results SEER criteria. We categorized patients by cancer type (15 major solid cancer groups and 3 major hematologic cancer groups), including pathological diagnosis, assessed latency periods, and relative risks (RRs) for developing MPCs. The overall MPC incidence was 2.3% . Breast cancer (15.7%) was the most common primary cancer, and lung cancer (15.2%) was the most frequent second primary cancer. The median latency period for second primary cancers was 4.1 years. Decreasing latency periods for third and fourth primary cancers were observed (2.1 years and 1.6 years, respectively) . Most cancers maintained their dominant pathological type despite notable changes in the prevalence of specific pathologies for certain types of second primaries. Lymphoma showed the highest RR (2.1) for developing MPCs. Significant associations were found between specific primary and subsequent cancers, including breast–ovary, thyroid–breast, stomach–pancreas, colorectal–head and neck, lung– pr","cbCaicqPm2ctRPfs","https://ap.wps.com/l/cbCaicqPm2ctRPfs","pdf",3192063,17,"English","# Abstract\n# 1. Introduction","[{\"question\":\"What is the main objective of the study on multiple primary cancers?\",\"answer\":\"To determine the incidence and clinical characteristics of multiple primary cancers at a single cancer center in Korea over a 20-year period.\"},{\"question\":\"How were multiple primary cancers identified in the analysis?\",\"answer\":\"Researchers retrospectively analyzed 96,174 cancer patients (2003–2022) and identified 2,167 metachronous MPC cases using Surveillance, Epidemiology, and End Results (SEER) criteria.\"},{\"question\":\"Which cancer types were most common as primary and second primary cancers?\",\"answer\":\"Breast cancer was the most common primary cancer (15.7%), while lung cancer was the most frequent second primary cancer (15.2%).\"},{\"question\":\"What factors or patterns did the study report regarding latency and relative risk?\",\"answer\":\"The median latency for second primaries was 4.1 years, with decreasing latency for third and fourth primaries (2.1 and 1.6 years). Lymphoma had the highest relative risk for developing MPCs (RR 2.1).\"}]","Incidence and Characteristics of Multiple Primary Cancers - A 20-Year Retrospective Study of a Single Cancer Center in Korea | PDF",1789990836,43]