1. Department of Epidemiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University , Okayama, Japan
2. Okayama University Thoracic Surgery Study Group (OUTSSG) , Okayama, Japan
3. Department of General Thoracic Surgery, Chugoku Central Hospital , Fukuyama, Japan
4. Department of Thoracic Surgery, Iwakuni Clinical Center , Iwakuni, Japan
5. Division of Thoracic Surgery, Yamaguchi-Ube Medical Center , Ube, Japan
6. Department of Thoracic Surgery, Hiroshima City Hiroshima Citizens Hospital , Hiroshima, Japan
7. Department of Thoracic Surgery, Shikoku Cancer Center , Matsuyama, Japan
8. Center of Chest Medicine and Surgery, Ehime University , Toon, Japan
9. Department of Thoracic Surgery, Kure Kyosai Hospital , Kure, Hiroshima, Japan
10. Department of Surgery, Tsuyama Chuo Hospital , Tsuyama, Okayama, Japan
11. Department of Thoracic Surgery, Japanese Red Cross Society Himeji Hospital , Okayama, Japan
12. Department of Thoracic Surgery, Japanese Red Cross Okayama Hospital , Himeji, Japan
13. Department of Thoracic Surgery, National Hospital Organization Okayama Medical Center , Japan
14. Department of Surgery, Onomichi Municipal Hospital , Onomichi, Japan