Feasibility of low-dose radiotherapy for patients with stage I/II extranodal NK-/T-cell lymphoma, nasal type achieving complete response after l-asparaginase-containing chemotherapy

Purpose: To assess treatment outcomes in patients with stage I/II extranodal NK-/T-cell lymphoma, nasal type (ENKTCL-NT) and the feasibility of low-dose radiotherapy (RT) for achieving complete response (CR, defined as showing no residual hypermetabolic uptake on positron emission tomography [PET] or no residual lesions on computed tomography [CT]) after l-asparaginase-containing chemotherapy (l-ASP). Materials and methods: Between 1992 and 2018, 76 patients with early-stage ENKTCL-NT who achieved CR or partial response (PR) after induction chemotherapy received adjuvant RT. RT doses (using biologically equivalent doses in 2 Gy fractions [EQD2]) and rates of local recurrence-free survival (LRFS), locoregional recurrence-free survival (LRRFS), distant metastasis-free survival (DMFS), progression-free survival (PFS), and cancer-specific survival (CSS) were determined. Results: Median follow-up was 5.1 years (range, 0.5–20.8). The median RT dose was 45 Gy (range, 20–54). The 5-year LRFS, LRRFS, DMFS, PFS, and CSS rates were 82.7 %, 78.2 %, 81.1 %, 68.7 %, and 84.4 %, respectively. CR after induction chemotherapy was notably linked to better survival outcomes across each endpoint. Survival outcomes were not affected either by the administration of l-ASP or EQD2