Intensity-modulated radiation therapy use for the localized treatment of thyroid cancer: Nationwide practice patterns and outcomes.

In the absence of randomized data, the optimal approach to adjuvant radiation therapy in locally advanced thyroid cancer remains unclear. We employed a large retrospective analysis to assess the best available evidence of a potential beneficial impact of intensity-modulated versus 3D-conformal radiotherapy (IMRT vs. 3D-CT). Retrospective analysis of adult thyroid cancer diagnosed between 2004 and 2011 within the National Cancer Database. Among patients treated with radiation therapy (N = 855), the use of IMRT (N = 437) increased among both comprehensive and academic centers (both p < 0.001), but not community hospitals (p = 0.43). Receipt of IMRT was associated with adverse clinical factors in multivariable analysis, including positive surgical margins, non-DTC histologies, and nodal metastases (all p < 0.001). IMRT use was associated with a significantly higher dose of radiation (60.7 vs. 52.4 Gy, p < 0.001). In multivariable analyses, receipt of IMRT demonstrated a trend toward improved overall survival (HR, 0.67; 95 % CI, 0.40-1.10; p = 0.115). This study presents the largest cohort to date examining receipt of IMRT in patients with locally advanced thyroid cancer and demonstrates an association between IMRT, treatment at a tertiary care center, higher total dose, and comparable or superior outcomes compared to patients treated with 3D conformal techniques despite more adverse disease features. In the absence of adequately powered prospective randomized trials, our retrospective analysis provides empirical evidence to support the use in these patients of dose escalation and IMRT, particularly at tertiary care centers.