Preliminary study of integrating pretreatment and early follow-up FDG-PET in patients with localized nasal natural killer/T-cell lymphoma receiving concurrent chemoradiotherapy

Background: The optimal treatment modality for stage I/II extranodal nasal natural killer/T-cell lymphoma (NKTL) including radiotherapy (RT) alone, concurrent, or sequential chemoradiotherapy and radiation doses were not well-defined. We aimed to evaluate early responses to concurrent chemoradiotherapy (CCRT) via image-guided tomotherapy for patients with NKTL and utilize uorine-18- uorodeoxyglucose positron emission tomography with computed tomography (FDG-PET/CT) for target delineation and response prediction. Methods: We retrospectively reviewed stage I/II extranodal nasal NKTL patients who received CCRT as primary treatment. The RT was 56 Gy in 28 fractions to gross disease and 50.4 Gy in 28 fractions to the involved-field using image-guided helical tomotherapy with intensity-modulated radiation therapy- simultaneous integrated boost technique. The chemotherapy consisted of three courses of dexamethasone, etoposide, ifosfamide, and carboplatin. FDG-PET/CT scans were performed before CCRT for RT target delineation and at 1 month following the treatment for response assessment. Early responses to CCRT and treatment-related toxicities were analyzed. Results: Four male patients who received CCRT were identi ed. After completion of CCRT, 4 (100%) patients achieved a complete response by CT and FDG-PET metabolic criteria. In FDG-PET metabolic responses between pre-CCRT and post-CCRT, the mean of maximum standardized uptake value (SUVmax) of tumors significantly declined from 18.25±3.77 to 2.38±0.34. The grade 3 toxicities of these four patients were leukopenia (50%) and oral mucositis (25%). At a median follow-up of 29 months (range, 21–33 months), 4 (100%) patients are currently alive in durable complete remission and disease-free status. Conclusions: Our reports suggest that CCRT with modern image-guided helical tomotherapy provides durable initial complete responses and tolerable side effects for patients with localized nasal NKTL. Integrated FDG-PET-guided RT is feasible for target delineation and response assessment.