3686 - Effects of Radiotherapy Techniques on Loco-Regional Recurrence in Patients with Early-Stage Extranodal NK/T-Cell Lymphoma
Presenter(s)
Y. Nakashima1, S. Takano1, N. Tomita1, T. Takaoka1, D. Okazaki1, M. Niwa1, A. Torii1, N. Kita1, Y. Hattori2, A. Miyakawa3, T. Matsui4, R. Murata5, S. Otsuka6, C. Sugie7, S. Ayakawa8, M. Iwana9, M. Iida10, M. Kuno11, S. Iida12, and A. Hiwatashi1; 1Department of Radiology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan, 2Department of Radiation Oncology, Nagoya Proton Therapy Center, Nagoya City University West Medical Center, Nagoya, Japan, 3Department of Radiation Oncology, National Hospital Organization Nagoya Medical Center, Nagoya, Japan, 4Department of Radiation Oncology, Konan Kosei Hospital, Konan, Japan, 5Department of Radiation Oncology, Suzuka General Hospital, Suzuka, Japan, 6Department of Radiology, Okazaki City Hospital, Okazaki, Japan, 7Department of Radiology, Japanese Red Cross Aichi Medical Center Nagoya Daini Hospital, Nagoya, Japan, 8Department of Radiation Oncology, Japan Community Health care Organization Chukyo Hospital, Nagoya, Japan, 9Department of Radiotherapy, Nagoya City University West Medical Center, Nagoya, Japan, 10Department of Radiology, Toyokawa City Hospital, Toyokawa, Japan, 11Department of Radiation Oncology, Ichinomiya Municipal Hospital, Ichinomiya, Japan, 12Department of Hematology and Oncology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
Purpose/Objective(s):
In the treatment for early-stage extranodal NK/T-cell lymphoma (ENKTCL), chemotherapy (CT) regimens have been extensively investigated. However, the impact of radiotherapy (RT)-related factors, such as intensity-modulated radiotherapy (IMRT), irradiation dose, and irradiation field, on outcomes remains unclear due to the extreme rarity of the disease. We aimed to identify clinical and therapeutic factors influencing loco-regional recurrence (LRR) in early-stage ENKTCL.Materials/Methods:
We identified 45 patients who received definitive IMRT or three-dimensional conformal radiation therapy (3DCRT) with or without CT for stage I/IIE ENKTCL from 2004 to 2023 at 10 institutions. Among these, 15 patients (33%) received 3DCRT, 22 (49%) IMRT, and 8 (18%) a combination of both. The median equivalent dose in 2-Gy fractions (EQD2) with a/ß = 10 was 50 Gy (range, 49.6–60.0 Gy). The most common regimen was concurrent RT with DeVIC (dexamethasone, etoposide, ifosfamide, and carboplatin) (67%, n = 30). Five patients (11%) received RT alone. The primary endpoint was LRR, analyzed using cumulative incidence curves with death as a competing risk. Overall survival (OS) and progression-free survival (PFS) rates were estimated using the Kaplan-Meier method. Univariate analysis was performed using Gray’s test for LRR and the log-rank test for OS and PFS. Variables with P <0.20 were included in multivariate analysis using Fine-Gray regression for LRR and Cox regression for OS and PFS.Results:
The median follow-up duration was 64.5 months. The response rates according to the International Workshop Criteria were: CR, 68%; PR, 25%; SD, 0%; and PD, 7%. The 5-year cumulative incidence of LRR was 18.4%. At the last follow-up, 8 patients had LRR: 7 had local recurrence, and 1 had both local and cervical lymph node recurrence. The 5-year OS and PFS rates were 59.5% and 53.2%, respectively. Distant metastasis occurred in 14 patients (31%). In univariate analysis, IMRT was associated with a marginally lower 5-year incidence of LRR compared to 3DCRT (8.8% vs. 27.1%; P = 0.057), while no significant differences were found for EQD2 =54Gy (P = 0.29), whole-neck irradiation (P = 0.50), boost irradiation (P = 0.53), clinical target volume including the whole involved paranasal sinuses (P = 0.76), and CT use (P = 0.35). Age >60 years (P = 0.050) and ECOG PS =1 (P = 0.034) were significantly associated with decreased OS. In multivariate analysis, IMRT showed a trend toward reducing LRR (Hazard ratio, 0.17; 95% CI, 0.02–1.27; P = 0.084).Conclusion:
IMRT was associated with a notable reduction in LRR in patients treated for ENKTCL, although the result was marginally significant. This may reflect improved target coverage with IMRT compared to 3DCRT, as suggested by dosimetric studies. Further analyses incorporating treatment planning data are needed to refine the role of IMRT in the treatment for ENKTCL.