S517
Clinical - Haemotology
ESTRO 2026
oncologists from the Japanese Radiation Oncology Study Group (JROSG). Patients with localized ENKL who underwent concurrent chemoradiotherapy using RT- DeVIC–based regimens between 2014 and 2021 were analyzed. LRC was estimated using the Kaplan–Meier method. The associations between stage and failure pattern (locoregional-only vs. combined locoregional and systemic progression) were evaluated using chi- square or Fisher’s exact tests, and the timing of locoregional failure was compared using the log-rank test. Results: A total of 149 patients with detailed radiotherapy data treated with RT-DeVIC were included in this analysis. The median age was 59 years (range, 13–82), and 106 (71%) were men. The Ann Arbor stage was I in 102 (68%) and II in 47 (32%). Treatment included 3D-CRT in 54 patients (36%), IMRT (including transitions from 3D- CRT) in 92 (62%), and proton therapy in 3 (2%), with a median total dose of 50 Gy (range, 50–60.4 Gy). The median follow-up was 35 months (range, 4–91). The 2- and 5-year LRC rates were 85% and 79%, respectively. Among 26 patients with locoregional failure, 15 (58%) had locoregional-only failure and 11 (42%) had combined locoregional and systemic progression. Systemic progression was more frequent in stage II than in stage I (75% vs. 28%; p = 0.038). Stage II disease showed earlier locoregional failure than stage I (median, 10 vs. 14 months; p = 0.021). Combined failure cases also showed earlier failure than locoregional-only cases (median, 10 vs. 19 months; p = 0.017). Conclusion: Although ENKL is traditionally divided into localized and advanced stages, our findings suggest that stage II localized ENKL may represent an intermediate subgroup. Stage II disease tended to show both a higher frequency of systemic progression and earlier locoregional failure, highlighting the potential need for intensified systemic therapy, in addition to locoregional treatment, to improve long-term disease control. Keywords: ENKL, locoregional failure, systemic progression
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Association between early locoregional failure and systemic progression in localized extranodal NK/T- cell lymphoma Senzo Taguchi 1 , Kana Miyazaki 2 , Ayumi Fujimoto 3 , Naoya Ishibashi 4 , Koichi Isobe 5 , Hitoshi Ito 6 , Michiko Imai 7 , Hiroki Kawaguchi 8 , Emiko Shimoda 9 , Toshinori Soejima 10 , Hiroshi Igaki 11 , Dai Maruyama 12 , Naoko Asano 13 , Ritsuro Suzuki 3 , Motoko Yamaguchi 14 , Yasuo Ejima 15 1 Department of Radiation Oncology, Cancer Institute Hospital, Japanese Foundation for Cancer Research, Tokyo, Japan. 2 Department of Hematology and Oncology, Mie University Graduate School of Medicine, Tsu, Japan. 3 Department of Hematology and Oncology, Shimane University Hospital, Izumo, Japan. 4 Department of Radiology, Nihon University School of Medicine, Tokyo, Japan. 5 Department of Radiology, Toho University Sakura Medical Center, Chiba, Japan. 6 Department of Radiation Oncology, National Hospital Organization Kyoto Medical Center, Kyoto, Japan. 7 Department of Radiation Oncology, Hamamatsu Medical Center, Shizuoka, Japan. 8 Department of Radiation Oncology, Kobe University Graduate School of Medicine, Hyogo, Japan. 9 Department of Radiation Oncology, Nara Medical University, Nara, Japan. 10 Department of Radiation Oncology, Kobe Minimally Invasive Cancer Center, Hyogo, Japan. 11 Department of Radiation Oncology, National Cancer Center Hospital, Tokyo, Japan. 12 Department of Hematology Oncology, Cancer Institute Hospital, Japanese Foundation for Cancer Research, Tokyo, Japan. 13 Department of Molecular Diagnostics, Nagano Prefectural Shinshu Medical Center, Suzaka, Japan. 14 Department of Hematological Malignancies, Mie University Graduate School of Medicine, Tsu, Japan. 15 Department of Radiology, Dokkyo Medical University Hospital, Shimotsuga, Japan Purpose/Objective: Concurrent chemoradiotherapy (RT-DeVIC) has improved locoregional control (LRC) in localized extranodal NK/T-cell lymphoma (ENKL). However, the patterns and timing of failure, particularly systemic progression, remain heterogeneous, especially in stage II disease. In clinical practice, localized ENKL is generally managed with locoregional treatment, whereas advanced-stage disease requires systemic therapy. This study aimed to clarify the characteristics and timing of locoregional failure in localized ENKL and to determine whether the failure pattern and timing differ between stage II and stage I disease. Material/Methods: This retrospective, multi-institutional study was conducted as part of the NKEA-Next project in collaboration with hemato-oncologists and radiation
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Consolidation radiotherapy for residual lesions after autologous stem-cell transplantation in patients with CNS lymphoma Jiaqi Fan 1 , Philipp Linde 1 , Simone Ferdinandus 1 , Johannes Rosenbrock 1 , Emmanouil Fokas 1 , Hendrik Dapper 1 , Christian Baues 2 1 Department of Radiation Oncology, Cyberknife and Radiation Therapy, Faculty of Medicine and University
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