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Special Article The Cancer Clinical Library Database (CCLD) from the Korea-Clinical Data Utilization Network for Research Excellence (K-CURE) Project
Sangwon Lee1orcid, Yeon Ho Choi1, Hak Min Kim1, Min Ah Hong1, Phillip Park1, In Hae Kwak1, Ye Ji Kang1, Kui Son Choi1,2, Hyun-Joo Kong1, Hyosung Cha1,2, Hyun-Jin Kim1, Kwang Sun Ryu1, Young Sang Jeon3, Hwanhee Kim3, Jip Min Jung3, Jeong-Soo Im1,4, Heejung Chae1,5,orcid

DOI: https://doi.org/10.4143/crt.2024.218
Published online: July 15, 2024

1National Cancer Control Institute, National Cancer Center, Goyang, Korea

2Graduate School of Cancer Science and Policy, National Cancer Center, Goyang, Korea

3Division of Data Promotion, Korea Health Information Service, Seoul, Korea

4Department of Preventive Medicine, Gachon University College of Medicine, Incheon, Korea

5Center for Breast Cancer, Research Institute and Hospital, National Cancer Center, Goyang, Korea

Correspondence: Heejung Chae, National Cancer Control Institute, National Cancer Center, 323 Ilsan-ro, Ilsandong-gu, Goyang 10408, Korea
Tel: 82-31-920-1716 Fax: 82-31-920-2799 E-mail: hchae21@ncc.re.kr
• Received: February 27, 2024   • Accepted: July 9, 2024

Copyright © 2024 by the Korean Cancer Association

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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  • The common data model (CDM) has found widespread application in healthcare studies, but its utilization in cancer research has been limited. This article describes the development and implementation strategy for Cancer Clinical Library Databases (CCLDs), which are standardized cancer-specific databases established under the Korea-Clinical Data Utilization Network for Research Excellence (K-CURE) project by the Korean Ministry of Health and Welfare. Fifteen leading hospitals and fourteen academic associations in Korea are engaged in constructing CCLDs for 10 primary cancer types. For each cancer type-specific CCLD, cancer data experts determine key clinical data items essential for cancer research, standardize these items across cancer types, and create a standardized schema. Comprehensive clinical records covering diagnosis, treatment, and outcomes, with annual updates, are collected for each cancer patient in the target population, and quality control is based on six-sigma standards. To protect patient privacy, CCLDs follow stringent data security guidelines by pseudonymizing personal identification information and operating within a closed analysis environment. Researchers can apply for access to CCLD data through the K-CURE portal, which is subject to Institutional Review Board and Data Review Board approval. The CCLD is considered a pioneering standardized cancer-specific database, significantly representing Korea’s cancer data. It is expected to overcome limitations of previous CDMs and provide a valuable resource for multicenter cancer research in Korea.
In recent years, the number of hospitals implementing clinical data warehouses (CDWs) has been steadily increasing. A CDW is a repository that stores and manages vast amounts of clinical data collected from various sources within a healthcare organization [1]. CDWs play a crucial role in healthcare research by enabling comprehensive data integration, standardization, and analysis. Moreover, several common data models (CDMs) have been developed to facilitate the effective utilization of data on a multicenter basis. These CDMs provide standardized database schemas that can be applied to healthcare data from diverse organizations with varying structures. For example, the Observational Medical Outcomes Partnership (OMOP) CDM is widely adopted to standardize and facilitate efficient large-scale analysis of medical data [2].
Despite the recent advances in the OMOP CDM and its extensive coverage of healthcare domains, it has limitations in the field of cancer research [3]. It still lacks a comprehensive data model specifically designed for cancer that can effectively capture cancer stage at diagnosis, treatment, and outcomes [4]. In addition, the processing of CDW data poses a major challenge for researchers, as CDWs are typically designed to minimize information loss from source data rather than to provide data tailored to the needs of back-end users. The significant time and effort required for data preprocessing are increasingly problematic in the era of machine learning, which demands access to a substantial volume of diverse clinical data.
In this context, the Korean Ministry of Health and Welfare launched the Korea-Clinical Data Utilization Network for Research Excellence (K-CURE) project in 2022, with the primary objectives of establishing cancer-specific common databases called Cancer Clinical Library Databases (CCLDs) and promoting collaborative multicenter studies. Fifteen leading hospitals in Korea are participating in the K-CURE project to establish standardized CCLDs (Fig. 1). These hospitals are in the process of establishing in-hospital CCLDs for the following 10 primary cancer types: breast, gastric, colorectal, liver, lung, prostate, pancreatic, kidney, cervical, and hematological malignancies.
The K-CURE CCLD steering committee, comprising representatives from the 15 hospitals, is responsible for project governance, including determining essential project policies and encouraging collaborative efforts. It has established two committees to handle practical project operations—the Cancer Data Standards and Quality Committee is tasked with defining clinical data items and maintaining quality control, while the Cancer Data Construction and Utilization Committee is entrusted with enhancing clinical data accessibility and utilization.
1. Plan for CCLD construction
The K-CURE project plans to establish CCLDs for 10 primary cancer types from 2022 to 2025, with breast and gastric cancer in 2022, colorectal and liver cancer in 2023, lung, pancreatic, and prostate cancer in 2024, and kidney, cervical, and hematological malignancies in 2025. Each year, participating hospitals choose at least one cancer-specific CCLD to establish. As of 2023, the CCLDs for breast, gastric, colorectal, and liver cancer have been completed. The CCLDs for the remaining cancer types will be completed by 2025. Updated information on the CCLD establishment status by hospital is available at the following link: https://k-cure.mohw.go.kr/.
2. Population
Each CCLD for a specific cancer type comprises patients diagnosed with that cancer after 2010, as per the National Cancer Registration Program, with the primary tumor site classified according to the International Classification of Diseases for Oncology, 3rd edition (ICD-O-3) [5]. For example, the CCLDs for gastric cancer include patients who were initially registered in a hospital’s cancer registry under code C16.x after 2010.
3. Selection and standardization of data items
Selection and standardization of data items are performed in two steps (Fig. 2). The first step, which was completed before the initiation of the K-CURE project, aimed to determine the data necessary for cancer research. Cancer experts from diverse academic societies/groups participated in this process, determining the key data items for the 10 cancer types and assessing their clinical importance and collectability. The National Cancer Data Center (NCDC) standardized the data items and profiles across the cancer types and published “Standard Item Definition Guidelines for Cancer” for each cancer type.
The second step involves determining which data items selected in step 1 can be extracted from real-world hospital records and designing a standard schema for each cancer type-specific CCLD. A Cancer Data Standards and Quality Committee is established for each cancer type containing at least one cancer doctor, one data scientist, and one health information manager from each participating hospital. The committee identifies extractable data from each hospital and discusses the standard schema for the CCLD from both a medical and data science perspective. Subsequently, the NCDC finalizes the standard schema for the CCLD. It then distributes the schema to the hospitals, who collect the clinical data on the patients. Quality control measures for CCLDs are in accordance with six-sigma principles [6].
4. Schema design and data collection
The CCLD data frame comprises an extensive set of tables and columns in which each patient’s comprehensive cancerrelated clinical data are collected throughout their entire diagnosis and treatment process (Fig. 3). The tables and columns comprise five types of clinical information: patient and tumor information, clinical assessment, test result, treatment, and follow-up (Fig. 4). For example, the CCLDs for breast and gastric cancers contain 23 tables with 513 columns and 22 tables with 498 columns, respectively. Most tables and columns are identical across all cancer types, but some are specific to a particular primary cancer type to reflect its unique features (Table 1). For instance, breast and gastric cancer CCLDs share tables for cancer characteristics and patient demographics, medical and family history, physical measurements, diagnostic information, laboratory and imaging tests, pathology results, treatment specifics, and followup data. Meanwhile, details on Helicobacter pylori infection and endoscopic submucosal dissection are exclusively collected in gastric cancer CCLDs, and tables for obstetric history, germline genetic tests, and gene expression assays are exclusively collected in breast cancer CCLDs. Each hospital establishes cancer-specific CCLDs with its own clinical data.
Subsequent to the establishment of a CCLD, hospitals not only update clinical data for the initial target population but also register newly diagnosed cancer patients on an annual basis (Fig. 5). For example, the breast and gastric CCLDs were established in 2022 and initially contained data from patients diagnosed with cancer from January 1, 2010, to December 31, 2021. Then, in 2023, the CCLDs were updated to include patients newly diagnosed with cancer in 2022. Additionally, clinical data from 2022 for patients already registered in the CCLDs were added.
CCLD data are pseudonymized to protect the privacy of patients and prevent potential risk of re-identification of individuals. In compliance with Korea’s Privacy Act, sharing personal information with a third party that could re-identify individuals from pseudonymized data is strictly prohibited. Consequently, the personal identifiable information of all patients included in a CCLD is de-identified by replacing names and social IDs with random characters. In addition, details regarding residential locations are excluded, and a patient’s date of birth is masked to contain only the year and month. Furthermore, the Ministry of Health and Welfare has published guidelines for the additional pseudonymization of medical data that can possibly re-identify individuals in the absence of personal identifiable information [7,8]. The K-CURE project also complies with these guidelines when providing CCLD data.
In addition, researchers can only access a hospital’s CCLD after securing approval from both the Institutional Review Board (IRB) and Data Review Board (DRB) of that hospital, ensuring adherence to ethical and privacy standards. Once a researcher has secured approval, a data engineer curates the database to the study’s specific population as defined in the research protocol. This data provisioning, which involves data filtering, customization, and combination, is conducted in a secure, restricted area to minimize any risk of patient privacy breaches. Analysis of CCLD data is permitted exclusively in designated secure locations reinforcing the commitment to data integrity and confidentiality. Additionally, once all analyses are complete, researchers can only retrieve the analysis results after undergoing another review to ensure the results do not contain any information that could potentially re-identify individuals in the study population.
Through the K-CURE project, researchers are able to access CCLDs from multiple hospitals for their studies (Fig. 6). (1) Researchers visit the K-CURE portal and explore summary statistics of and metadata about the CCLDs established by each hospital and decide which CCLDs to use. The CCLD summary statistics include details about the target population size and crucial clinical data, such as diagnosis, treatment, and pathologic information. Information is available at different levels: the general public, defined as anyone who visits the portal, can assess the basic demographic information such as age and sex; researchers who wish to use a CCLD for a study can access more detailed statistical summaries relevant to cancer research. (2) Researchers recruit collaborators from the candidate institutions. (3) Subsequently, researchers must obtain approval by the IRB and the DRB of the respective hospitals to ensure the planned study is unlikely to raise ethics or privacy issues. (4) These approvals are submitted to the K-CURE portal. (5) Data engineers from each hospital then extract customized data from their CCLD and transfer them to a Central Data Center which is a physically secure environment with a protected network. (6) Finally, researchers can access and analyze the data at the Central Data Center. Once researchers complete their analyses, they are only allowed to retrieve their results, preventing any risk of re-identification.
The K-CURE CCLDs are a significant representation of South Korea’s cancer data. The 15 major hospitals participating in the K-CURE project are pioneers in cancer care in the country. The Health Insurance Review and Assessment Service provides well-established guidelines for cancer diagnosis and treatment, consistently monitoring healthcare services to ensure they follow uniform standards, as the nation’s obligatory National Health Insurance covers the entire population [9-12]. Consequently, all hospitals consistently adhere to these guidelines. Collaborations among prominent, high-volume hospitals and the uniform nature of the Korean healthcare system ensure the representativeness of K-CURE CCLDs, which have great potential to continue building Korea’s cancer care research capabilities and improving outcomes. The CCLD summary statistics available at the K-CURE portal aid researchers in assessing and identifying the datasets most suitable for their study. Additionally, because CCLDs are standardized and designed for a specific cancer type, researchers can minimize the amount of time they spend preprocessing and consolidating data. Finally, allowing access to CCLD data exclusively in a centralized secure environment reduces the need for extensive pseudonymization. When researchers consolidate multi-hospital data outside the K-CURE system, they receive heavily pseudonymized data, which can limit the detail and value of their analyses.
However, there are several limitations to the CCLDs. First, hospitals having the discretion to select which data items to include led to variations in the types and amounts of data collected. In the real world, where each institution uses a different healthcare information system, differences in collectable data are inevitable. To minimize this disparity, the Cancer Data Standards and Quality Committee provided guidance, suggesting that hospitals gather data items that can be extracted in a structured format. Furthermore, all hospitals are required to achieve a collection rate of at least 60% and strive to improve their collection rate each year. Metadata information on the tables and columns collected by each institution is now available and will be updated annually on the K-CURE portal. Second, multicenter research can be hindered by a complex approval process. Researchers must obtain approval from the IRB and DRB at every participating hospital. However, this is the first national initiative that provides researchers with access to clinical data from hospitals. The Korean government continues to work toward simplifying the approval process while ensuring legal compliance.
In conclusion, in this article, we introduce the CCLD, a pioneering standardized cancer-specific database that overcomes the limitations of previous CDWs. The use of clinical data has traditionally encountered challenges pertaining to limited accessibility due to privacy concerns and issues with unstructured data across multiple sites. We have addressed these challenges by creating standardized cancer-specific CCLDs containing de-identified information. These CCLDs are exclusively assessable via a secure environment. The CCLDs are Korea’s largest-scale clinical cancer databases and are the result of a collaborative effort by experts in oncology, healthcare, and data science from leading hospitals across South Korea. We aim to have CCLDs established for ten primary cancers by 2025. Their successful development holds significant promise as a valuable resource for multicenter cancer research.

Author Contributions

Conceived and designed the analysis: Choi KS, Kong HJ, Cha H, Kim HJ, Ryu KS, Jeon YS, Kim H, Jung JM, Im JS, Chae H.

Collected the data: Lee S, Choi YH, Kim HM, Hong MA, Park P, Kwak IH, Kang YJ, Choi KS, Ryu KS, Jeon YS, Kim H, Jung JM, Im JS, Chae H.

Contributed data or analysis tools: Lee S, Choi YH, Kim HM, Hong MA, Park P, Kwak IH, Kang YJ, Choi KS, Kong HJ, Cha H, Kim HJ, Ryu KS, Jeon YS, Kim H, Jung JM, Im JS, Chae H.

Performed the analysis: Lee S, Choi YH, Kim HM, Hong MA, Park P, Kwak IH, Kang YJ, Chae H.

Wrote the paper: Lee S, Chae H.

Conflicts of Interest

Conflict of interest relevant to this article was not reported.

Acknowledgements
We would like to express our gratitude to the Korean Ministry of Health and Welfare and the Korea Health Information Service for their support of the K-CURE project. We extend our thanks to the 15 participating hospitals in Korea (National Cancer Center Korea, Asan Medical Center, Samsung Medical Center, Seoul National University Hospital, Severance Hospital, Korea University Anam Hospital, Pusan National University Hospital, Seoul National University Bundang Hospital, Ajou University Hospital, Gachon University Gil Medical Center, Konyang University Hospital, Hallym University Sacred Heart Hospital, Jeonbuk National University Hospital, Chonnam National University Hwasun Hospital, and Daegu Catholic University Medical Center) for their substantial involvement in the development of the CCLD. We also acknowledge the valuable contributions of academic associations (Korean Breast Cancer Society, Korean Gastric Cancer Association, Korean Liver Cancer Association, Korean Society of Coloproctology, Korean Association for Lung Cancer, Korean Association for Thoracic Surgical Oncology, Korean Prostate Society, Korean Urological Oncology Society, Association of Hepato-Biliary-Pancreatic Surgery, Korean Pancreatobiliary Association, Korean Society of Pediatric Hematology-Oncology, Korean Society of Gynecologic Oncology, Korean Society of Medical Oncology, Korean Society for Radiation Oncology) in defining the “Standard Item Definition Guidelines for Cancer.” This paper is supported by the Ministry of Health and Welfare (No. 22A2400-1).
Fig. 1.
Hospitals participating in the Korea-Clinical Data Utilization Network for Research Excellence (K-CURE) project. Fifteen hospitals across different regions in Korea are in the process of establishing Cancer Clinical Library Databases (CCLDs) as a part of the K-CURE project.
crt-2024-218f1.jpg
Fig. 2.
Overview of the two-step Cancer Clinical Library Database (CCLD) data item standardization process. In the first step, items were listed based on their importance for cancer research in collaboration with academic societies. In the second step, the final items have been selected considering the feasibility of collection by hospitals. followed by the creation of a standard schema for the CCLDs by the Cancer Data Standards and Quality Committee. EMR, electronic medical record; K-CURE, Korea-Clinical Data Utilization Network for Research Excellence.
crt-2024-218f2.jpg
Fig. 3.
Storage of patient clinical information. Patient clinical data is collected and stored in the respective tables throughout the entire diagnosis, treatment, and follow-up process.
crt-2024-218f3.jpg
Fig. 4.
Overview of cancer type-specific hospital Cancer Clinical Library Database (CCLD) establishment process. Hospitals extract cancer patient data from their built-in clinical data warehouses (CDW) and store the information in a cancer type-specific CCLD. ICD-O-3, International Classification of Diseases for Oncology, 3rd edition.
crt-2024-218f4.jpg
Fig. 5.
Initial collection and update of data for Cancer Clinical Library Databases (CCLDs). Initial collection and update of data for CCLDs. A CCLD initially collects patient clinical data from 2010 to the year before its establishment. Following its establishment, the CCLD is updated to include. Subsequent follow-up data as well as data for newly registered patients on an annual basis.
crt-2024-218f5.jpg
Fig. 6.
Procedure for using Cancer Clinical Library Databases (CCLDs) for multicenter cancer research. Researchers are allowed to access to CCLD data after obtaining Institutional Review Board (IRB) and Data Review Board (DRB) approval. Analyses on the data may only be performed in a secured environment. K-CURE, Korea-Clinical Data Utilization Network for Research Excellence.
crt-2024-218f6.jpg
Table 1.
Description of data items collected in Cancer Clinical Library Databases (CCLDs)
Class Contents
Patient health information Cancer characteristics and patient demographic collected from the National Cancer Registration Program, medical history, alcohol and smoking habit, family history
- Items specific to breast cancer: obstetric history
Clinical assessment Physical measurement, performance status, chief complaint, diagnosis, clinical staging, metastasis
Test result Laboratory test, imaging test, biopsy and surgical pathology
- Items specific to breast cancer: germline genetic test, gene expression test
- Items specific to gastric cancer: Helicobacter pylori test, esophagogastroscopy, endoscopic ultrasound
Treatment Surgery, radiation therapy, systemic therapy, other medication, transfusion, treatment-related complication
- Items specific to gastric cancer: endoscopic resection
Follow-up observation Hospital visit, recurrence, death
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      The Cancer Clinical Library Database (CCLD) from the Korea-Clinical Data Utilization Network for Research Excellence (K-CURE) Project
      Image Image Image Image Image Image
      Fig. 1. Hospitals participating in the Korea-Clinical Data Utilization Network for Research Excellence (K-CURE) project. Fifteen hospitals across different regions in Korea are in the process of establishing Cancer Clinical Library Databases (CCLDs) as a part of the K-CURE project.
      Fig. 2. Overview of the two-step Cancer Clinical Library Database (CCLD) data item standardization process. In the first step, items were listed based on their importance for cancer research in collaboration with academic societies. In the second step, the final items have been selected considering the feasibility of collection by hospitals. followed by the creation of a standard schema for the CCLDs by the Cancer Data Standards and Quality Committee. EMR, electronic medical record; K-CURE, Korea-Clinical Data Utilization Network for Research Excellence.
      Fig. 3. Storage of patient clinical information. Patient clinical data is collected and stored in the respective tables throughout the entire diagnosis, treatment, and follow-up process.
      Fig. 4. Overview of cancer type-specific hospital Cancer Clinical Library Database (CCLD) establishment process. Hospitals extract cancer patient data from their built-in clinical data warehouses (CDW) and store the information in a cancer type-specific CCLD. ICD-O-3, International Classification of Diseases for Oncology, 3rd edition.
      Fig. 5. Initial collection and update of data for Cancer Clinical Library Databases (CCLDs). Initial collection and update of data for CCLDs. A CCLD initially collects patient clinical data from 2010 to the year before its establishment. Following its establishment, the CCLD is updated to include. Subsequent follow-up data as well as data for newly registered patients on an annual basis.
      Fig. 6. Procedure for using Cancer Clinical Library Databases (CCLDs) for multicenter cancer research. Researchers are allowed to access to CCLD data after obtaining Institutional Review Board (IRB) and Data Review Board (DRB) approval. Analyses on the data may only be performed in a secured environment. K-CURE, Korea-Clinical Data Utilization Network for Research Excellence.
      The Cancer Clinical Library Database (CCLD) from the Korea-Clinical Data Utilization Network for Research Excellence (K-CURE) Project
      Class Contents
      Patient health information Cancer characteristics and patient demographic collected from the National Cancer Registration Program, medical history, alcohol and smoking habit, family history
      - Items specific to breast cancer: obstetric history
      Clinical assessment Physical measurement, performance status, chief complaint, diagnosis, clinical staging, metastasis
      Test result Laboratory test, imaging test, biopsy and surgical pathology
      - Items specific to breast cancer: germline genetic test, gene expression test
      - Items specific to gastric cancer: Helicobacter pylori test, esophagogastroscopy, endoscopic ultrasound
      Treatment Surgery, radiation therapy, systemic therapy, other medication, transfusion, treatment-related complication
      - Items specific to gastric cancer: endoscopic resection
      Follow-up observation Hospital visit, recurrence, death
      Table 1. Description of data items collected in Cancer Clinical Library Databases (CCLDs)


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