The impact of the omission or inadequate dosing of radiotherapy in extranodal natural killer T-cell lymphoma, nasal type, in the United States

Abstract

Background: Extranodal natural killer T-cell lymphoma, nasal-type (NKTCL), is a rare malignancy in Western populations and is thus challenging for standardization of care and a prospective study. This study was aimed at defining patterns of care for NKTCL in the context of radiotherapy (RT) use and dose selection in the United States.

Methods: Six hundred forty-two stage I-II NKTCL patients from 1998 to 2012 were identified from the National Cancer Data Base. Binary logistic regression analyses were performed to identify sociodemographic, treatment, and tumor characteristics predictive of the treatment selection and RT dose. Overall survival (OS) analyses were completed with the Kaplan-Meier and Cox multivariate methods, including a propensity score adjustment for a potential indication bias.

Results: Of the 642 included NKTCL patients, 70% were at stage I, 79% were white, and 66% were ≤ 60 years old. Fifty-five percent received chemotherapy plus RT, 19% received RT alone, and 27% received chemotherapy alone. The median RT dose was 50 Gy (interquartile range, 43.2-54 Gy), 37% received < 45 Gy, and 43% received < 50 Gy. A multivariate survival analysis showed improved OS in comparison with chemotherapy alone for RT alone at ≥50 Gy (hazard ratio [HR], 0.41; 95% confidence interval [CI], 0.23-0.70; P < .01), for chemotherapy plus RT at <50 Gy (HR, 0.55, 95% CI, 0.36-0.86; P < .01), and for chemotherapy plus RT at ≥50 Gy (HR, 0.41; 95% CI, 0.27-0.63; P < .01).

Conclusions: Stage I-II NKTCL patients in the United States commonly receive chemotherapy alone or suboptimal-dose RT. The omission of RT or the use of suboptimal RT is negatively associated with OS. Efforts to continue improving evidenced-based management are warranted. Cancer 2017;123:3176-85. © 2017 American Cancer Society.

Keywords: 45 Gy; 50 Gy; National Cancer Data Base (NCDB); natural killer (NK) T-cell lymphoma; radiation dose response; radiation therapy.