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Abstract
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.

Adverse event profile after radiotherapy for patients with stage I/II extranodal NK-/T-cell lymphoma, nasal type.

Abbreviations: L-ASP, L-asparaginase-containing chemotherapy; EQD2, equivalent dose in 2 Gy fractions; 3D-CRT, Three-dimensional conformal radiation therapy; IMRT, intensity-modulated radiation therapy; Gr, grade.

Affiliations

Jae Sik Kim 1 2, Noorie Choi 3, Il Han Kim 1, Tae Min Kim 4 5, Yoon Kyung Jeon 5 6, Ji Hyun Chang 1 7
1Department of Radiation Oncology, Seoul National University College of Medicine, Seoul, Republic of Korea.
2Department of Radiation Oncology, Soonchunhyang University Seoul Hospital, Seoul, Republic of Korea.
3Department of Radiation Oncology, Veterans Health Service Medical Center, Seoul, Republic of Korea.
4Department of Internal Medicine, Seoul National University Hospital, Seoul, Republic of Korea.
5Seoul National University Cancer Research Institute, Seoul National University College of Medicine, Seoul, Republic of Korea.
6Department of Pathology, Seoul National University Hospital, Seoul, Republic of Korea.
7Department of Radiation Oncology, Seoul National University Hospital, Seoul, Republic of Korea.