S532
Clinical – Head & neck
ESTRO 2026
Material/Methods: Patients (pts) aged 20-80 years with T1-2N0-1M0 (UICC 7th 2009) OPC (tonsil, base of tongue and soft palate) with performance status 0-1 were enrolled. Chemotherapy was not permitted. As adaptive two- step IMRT, computed tomography planning was performed twice before IMRT for the initial plan of 46 Gy/23 fractions (fr) and during treatment for the boost plan of 24 Gy/12 fr with a total dose of 70 Gy/35 fr. The extent of prophylactic irradiation to the contralateral internal jugular chain was omitted (ipsilateral irradiation) if the primary lesion was the tonsil, and only levels II-III if the base of tongue and soft palate. This analysis was conducted 5 years after the last enrollment. Results: Between June 2014 and July 2020, 57 pts (tonsil: 46 pts, base of tongue: 4 pts, soft palate: 7 pts) were enrolled from 23 institutions. The pts consisted of 36 male and 21 female with the median age of 68 years (range, 41- 80). T1/2 pts were 11/46, N0/1 pts were 31/26, and Stage I/II/III pts were 6/25/26. At a median follow-up of 6.8 years, 13 deaths were reported (4 disease-related, 6 due to other causes, 1 treatment-related). The 5-year OS was 88% [95% CI 76%-94%]. The 5-year PFS and loco-regional PFS were 77% [95% CI 64-86%] and 79% [95% CI 66-87%]. There were seven loco-regional recurrences, none from outside the minimally established prophylactic irradiation area. No Grade 3-5 late adverse reactions were observed. Grade ≥ 2 late toxicity (excluding hypothyroidism) occurred in 32% (18/56). Cumulative Grade ≥ 2 hypothyroidism was 12% (6/50) at 5 years. Conclusion: The 5-year results of JCOG1208 demonstrated that IMRT alone with reduced dose and minimized prophylactic target volumes achieved excellent long- term survival and loco-regional control with minimal toxicity in early-stage oropharyngeal cancer. This trial provides strong prospective evidence to support the use of this de-intensified strategy as a function- preserving approach for appropriately selected patients. References: Garden AS, et al. Final Report of NRG Oncology RTOG 0022: A Phase 1/2 Study of Conformal and Intensity Modulated Radiation for Oropharyngeal Cancer. Int J Radiat Oncol Biol Phys 117: 333-340, 2023. Keywords: oropharyngeal cancer, IMRT alone
Mini-Oral 260
Five-year follow-up outcomes from JCOG1208: A single-arm confirmatory trial of IMRT alone for early-stage oropharyngeal cancer Satoaki Nakamura 1 , Takeshi Kodaira 2 , Ryosuke Kato 3 , Takeo Nakashima 4 , Yoshinori Ito 5 , Naoki Nakamura 6 , Satoshi Ishikura 7 , Takashi Toshiyasu 8 , Yoshihiro Saito 9 , Satoru Takahashi 10 , Yosuke Ota 11 , Masahiro Inada 12 , Yuji Murakami 13 , Nobuteru Kubo 14 , Yuta Sekino 3 , Haruhiko Fukuda 3 , Yasumasa Nishimura 12 , Takashi Mizowaki 15 1 Radiology, Kansai Medical University, Hirakata, Japan. 2 Radiation Oncology, Aichi Cancer Center, Nagoya, Japan. 3 JCOG Data Center/Operation Office, National Cancer Center Hospital, Tokyo, Japan. 4 Clinical Practice and Support, Hiroshima University Hospital, Hiroshima, Japan. 5 Radiation Oncology, Showa Medical University School of Medicine, Tokyo, Japan. 6 Radiation Oncology, St. Marianna University School of Medicine, Tokyo, Japan. 7 Radiation Oncology, St. Luke’s International Hospital, Tokyo, Japan. 8 Radiation Oncology, Cancer Institute Hospital of JFCR, Tokyo, Japan. 9 Radiation Oncology, Saitama Cancer Center, Saitama, Japan. 10 Radiation Oncology, Jichi Medical University, Shimotsuke, Japan. 11 Radiation Oncology, Hyogo Cancer Center, Akashi, Japan. 12 Radiation Oncology, Kindai University, Sakai, Japan. 13 Radiation Oncology, Hiroshima University, Hiroshima, Japan. 14 Radiation Oncology, Gunma University Graduate School of Medicine, Maebashi, Japan. 15 Radiation Oncology and Image-Applied Therapy, Kyoto University, Graduate School of Medicine, Kyoto, Japan Purpose/Objective: Few homogeneous prospective datasets have reported long-term survival outcomes of patients with early-stage oropharyngeal cancer (OPC) treated with radiotherapy alone. The Japan Clinical Oncology Group conducted JCOG1208, a multicenter single-arm confirmatory phase III trial, to evaluate the efficacy and safety of two-step adaptive intensity-modulated radiotherapy (IMRT) with reduced dose and minimized prophylactic target volumes. The primary analysis results with 3-year follow-up have been previously reported. After a protocol amendment, an extended follow-up was planned to assess long-term outcomes. This report presents the 5-year outcomes.
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