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 < 40 Gy in patients displaying CR after l-ASP. Adverse events (AEs) ≥ Grade 2 were significantly reduced with EQD2 < 40 Gy, compared with EQD2 ≥ 40 Gy.
Conclusion: Achieving CR after chemotherapy was the most predictive factor of survival outcomes in early-stage ENKTCL-NT. Decreasing RT doses in patients with CR after l-ASP appeared to minimize the occurrence of AE without compromising LRR risk; however, longer follow-ups and cautious application are warranted.
Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(© 2022 The Author(s).)