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Abstract
PURPOSE:
The purpose of this study was to investigate the effect of hospital case volume on clinical outcomes in patients with nasopharyngeal carcinoma (NPC).

Materials and Methods:
Data on 1,073 patients with cT1-4N0-3M0 NPC were collected from a multi-institutional retrospective database (KROG 11-06). All patients received definitive radiotherapy (RT) either with three-dimensional-conformal RT (3D-CRT) (n=576) or intensity-modulated RT (IMRT) (n=497). The patients were divided into two groups treated at high volume institution (HVI) (n=750) and low volume institution (LVI) (n=323), defined as patient volume ≥ 10 (median, 13; range, 10 to 18) and < 10 patients per year (median, 3; range, 2 to 6), respectively. Endpoints were overall survival (OS) and loco-regional progression-free survival (LRPFS).

RESULTS:
At a median follow-up of 56.7 months, the outcomes were significantly better in those treated at HVI than at LVI. For the 614 patients of propensity score-matched cohort, 5-year OS and LRPFS were consistently higher in the HVI group than in the LVI group (OS: 78.4% vs. 62.7%, p < 0.001; LRPFS: 86.2% vs. 65.8%, p < 0.001, respectively). According to RT modality, significant difference in 5-year OS was observed in patients receiving 3D-CRT (78.7% for HVI vs. 58.9% for LVI, p < 0.001) and not in those receiving IMRT (77.3% for HVI vs. 75.5% for LVI, p=0.170).

CONCLUSION:
A significant relationship was observed between HVI and LVI for the clinical outcomes of patients with NPC. However, the difference in outcome becomes insignificant in the IMRT era, probably due to the standardization of practice by education.

Author information

Ha B1, Cho KH1, Moon SH1, Lee CG2, Keum KC2, Kim YS3, Wu HG4, Kim JH4, Ahn YC5, Oh D5, Noh JM5, Lee JH6, Kim SH6, Kim WT7, Oh YT8, Kang MK9, Kim JH10, Kim JY11, Cho MJ12, Kay CS13, Choi JH14.
1
Proton Therapy Center, Research Institute and Hospital, National Cancer Center, Goyang, Korea.
2
Department of Radiation Oncology, Yonsei University College of Medicine, Seoul, Korea.
3
Department of Radiation Oncology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
4
Department of Radiation Oncology, Seoul National University College of Medicine, Seoul, Korea.
5
Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
6
Department of Radiation Oncology, St. Vincent's Hospital, College of Medicine, The Catholic University of Korea, Suwon, Korea.
7
Department of Radiation Oncology, Pusan National University Hospital, Busan, Korea.
8
Department of Radiation Oncology, Ajou University School of Medicine, Suwon, Korea.
9
Department of Radiation Oncology, School of Medicine, Kyungpook National University, Daegu, Korea.
10
Department of Radiation Oncology, Dongsan Medical Center, Keimyung University School of Medicine, Daegu, Korea.
11
Department of Radiation Oncology, Yeouido St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
12
Department of Radiation Oncology, Chungnam National University School of Medicine, Daejeon, Korea.
13
Department of Radiation Oncology, Incheon St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Incheon, Korea.
14
Department of Radiation Oncology, Chung-Ang University Hospital, Seoul, Korea.