Postoperative simultaneous integrated boost-intensity modulated radiation therapy for patients with locoregionally advanced papillary thyroid carcinoma: preliminary results of a phase II trial and propensity score analysis.

ABSTRACT

CONTEXT With recent technical advances in radiotherapy (RT) planning, simultaneous integrated boost intensity modulated radiotherapy (SIB-IMRT) has made possible the delivery of high radiation dose to the tumor, minimizing surrounding normal tissues. OBJECTIVE: This study aimed to evaluate the clinical effectiveness and safety of postoperative SIB-IMRT in patients with locoregionally advanced papillary thyroid cancer (PTC). DESIGN AND SETTING: This was a propensity score-matched case control study conducted at a tertiary referring center. PATIENTS OR OTHER PARTICIPANTS: This study included locoregionally advanced patients with PTC (pT4 or N1b) who underwent thyroid cancer surgery and radioactive iodine ablation (RIA) followed by postoperative SIB-IMRT (RT group) under a phase II trial or no postoperative RT (Non-RT group) Intervention Postoperative SIB-IMRT was the intervention. MAIN OUTCOME MEASURES: locoregional relapse-free survival (LRFS) was compared between RT group and Non-RT group. RESULTS: Multivariate analysis showed that several factors, including sex, American Thyroid Association risk category, and use of postoperative RT were significantly associated with LRFS in all 201 patients (P < .05 each). In the 118 propensity score-matched patients, there were no significant differences in baseline characteristics between the RT and Non-RT groups, but the LRFS rate was significantly higher in the RT than in the Non-RT group (4 y 100% vs 84.6%, P = .002). Overall, SIB-IMRT was well tolerated, with no grade ≥3 toxicity, and was completed as planned in all patients. CONCLUSIONS: Postoperative SIB-IMRT is feasible and effective in improving locoregional control in patients with locally advanced PTC. Large-scale randomized studies are warranted.