PCSaudits were performed for 29 institutions. Based on the facility survey by Tsunemoto, 13 institutes were classified as A1 (university hospital/cancer centertreating >300 patients/year), 10 as B1 (otherinstitutes>120patients/year) and six as B2 (other institutes <120 patients/year). Medical charts for 455 patients with thoracic esophageal cancer between 1992 and 1994were reviewed based on the data format of PCS in the USA. Results: Concerning external beam equipment, linear accelerators of~1 0 MV were used for 73% of patients in A1, whereas in 81-2, 60CO machines were still used for 13%of patients (P< 0.0001). The median number of full-time equivalent (FTE) radiation oncologists was 2.7 in A1, 0.65 in B1 and 0.2 in B2. Forty-five percent of patients had received surgery in A1 and 34% in 81-2 (P= 0.0068).In the non-surgery group, a higher radiation dose of >60 Gy was delivered in A1 than in B1-2 (P = 0.0008). Chemotherapy was administered to 51 % of the patients in A1 and to 30% in B1-2 (P < 0.0001). Brachytherapy was utilized for 17% in A1 and only for 5% in B1-2 (P= 0.0001). Conclusion: Institutional stratification, including equipment andpersonnel, significantly affected the patterns of care for esophageal cancer. Therefore, to improve the quality of radiation therapy nationwide, improvement ofequipment andsupply of FTEpersonnel isextremely important. PCS was found to have great potential for the practical evaluation of how much will be required in Japan.Key words: Patterns ofCare Study -esophageal cancer -radiation therapy -quality assurance -structure offacility -radiation oncology equipment -radiation oncology personnel Received November 10,1997; accepted February 12, 1998 For reprints and all correspondence: Teruki Teshima, Department of Radiation Oncology, Osaka University Medical School, 2-2, Yamadaoka, Suita 565-0871, Japan. E-mail: teshima@sahs.med.osaka-u.ac.jp Abbreviations: PCS, Patterns of Care Study; QA, quality assurance; FTE, full-time equivalent; AJCC, American Joint Committee on Cancer; KPS, Karnofsky Performance Status; AI, university hospital/cancer center treating ;::300 patients/year; B1, other institutions treating ;::20patients/year; B2, other institutions treating < 120 patients/year INTRODUCTION Radiation therapy is expected to play an important role in cancer management in the next century because of a rapid increase in the number of elderly patients in Japan. These patients are generally not suitable candidates for aggressive surgery or chemotherapy. In the field of radiation oncology, many innovative techniques such as conformal therapy, intraoperative radiation therapy and heavy ion medical accelerator therapy have been developed by pioneers in Japan. However, basic treatment using photons, which is currently used to treat 99% of the candidates for radiation therapy, is not sophisticated enough. A structure survey of radiation oncology in 1990 by Tsunemoto (1) and a subsequent comparative study between the USA and Japan (2) showed that more than 60% of institutions in Japan we...