Dosimetric and clinical results of three-dimensional conformal radiotherapy for locally recurrent nasopharyngeal carcinoma

Abstract

PurposeTo assess the dosimetric and clinical results of three-dimensional conformal radiotherapy (3D CRT) for locally recurrent nasopharyngeal carcinoma (NPC). MethodsA total of 86 patients with locally recurrent NPC were retreated with 3D CRT. The median prescribed dose was 68Gy with 2Gy per fractionation. Dosimetric quality was evaluated with dose distribution in planning target volume (PTV) and specified organs at risk (OAR), dose conformity index (CI) and dose homogeneity index (HI). The actuarial rate of local failure-free (LFF), overall survival (OS) and major late toxicities (MLT) were estimated with Kaplan–Meier method. Multivariate analysis for prognosis was performed using the Cox regression proportional hazards model. ResultsThe mean dose to PTV averaged 66.8Gy, and the dose to specified OAR was acceptable. The average value of CI and HI was 0.59 and 9.1%. The 5-year actuarial rate of LFF and OS was 71 and 40%, respectively. The 5-year actuarial incidence of MLT≥Grade 3 and ≥Grade 4 were 100 and 49%, respectively. The major prognostic factors were T stage and the size of gross tumor volume (GTV). Advanced T stage and large GTV volume were associated with poor LFF and OS and high risk of MLT. ConclusionThe dosimetric quality of 3D CRT for locally recurrent NPC is generally excellent. A relatively high local control was achieved with this technique. However, the incidence of late toxicities were not found to decrease as originally expected. Early diagnosis of the recurrence and reasonable definition of the target volume are crucial to achieve a better outcome.