Intensity-modulated radiotherapy versus three-dimensional conformal radiotherapy for stage I-II natural killer/T-cell lymphoma nasal type: dosimetric and clinical results

BACKGROUND This study was to compare radiotherapy treatment planning and treatment outcomes following three-dimensional conformal radiotherapy (3DCRT) and intensity-modulated radiotherapy (IMRT) in stage I-II natural killer (NK)/T-cell lymphoma. METHODS The cases of 94 patients with stage I-II NK/T-cell lymphoma, nasal type in the upper aerodigestive tract who treated between May 2005 and Dec 2008 were reviewed. These patients received radiotherapy with or without induction chemotherapy. Definitive radiotherapy was conducted using 3DCRT in 47 patients and IMRT in the other 47 patients with a regional field and a total dose of 50 Gy. Dosimetric pmeters of radiation treatment plans, local control probability (LCP), overall survival (OS), and toxicities were analyzed and compared between 3DCRT and IMRT. RESULTS From the dosimetric analysis, IMRT demonstrated significantly better dose coverage and homogeneity than 3DCRT. However, after a median follow-up of 46 months, IMRT was not associated with improvements in 4y-OS (80.9% for 3DCRT vs. 82.7% for IMRT, p=0.87) or 4y-LCP (86.3% for 3DCRT vs. 88.9% for IMR p=0.85). Of the 18 patients who received cervical lymph node irradiation, those in the IMRT group received a lower mean parotid dose. Furthermore, at-risk organs were strictly kept within the safe dose range in both groups, and no severe late toxicity was observed. CONCLUSIONS IMRT provided better dose coverage than 3DCRT, although it failed to provide LCP and OS benefits. Definitive radiotherapy with a regional field and a total dose of 50 Gy is efficient and safe for NK/T-cell lymphoma using either IMRT or 3DCRT. However, IMRT may have the potential to reduce parotid gland hypofunction following cervical irradiation.