Clinical role of 18F-FDG PET/CT-based simultaneous modulated accelerated radiotherapy treatment planning for locally advanced nasopharyngeal carcinoma ⁎

Abstract

Abstract Objective The aim of this study was to compare the long-term local control, overall survival, and late toxicities of positron emission tomography/computed tomography (PET/CT)-guided dose escalation radiotherapy versus conventional radiotherapy in the concurrent chemoradiotherapy treatment of locally advanced nasopharyngeal carcinoma (NPC). Methods A total of 48 patients with stage III-IVa NPC were recruited and randomly administered PET/CTguided dose escalation chemoradiotherapy (group A) or conventional chemoradiotherapy (group B). The dose-escalation radiotherapy was performed using the simultaneous modulated accelerated radiotherapy technique at prescribed doses of 77 gray (Gy) in 32 fractions (f) to the gross target volume (GTV): planning target volume (PTV) 1 received 64 Gy/32 f, while PTV2 received 54.4 Gy/32 f. Patients in group B received uniform-dose intensity-modulated radiotherapy, PTV1 received 70 Gy/35 f and PTV2 received 58 Gy/29 f. Concurrent chemotherapy consisted of cisplatin [20 mg/m2 intravenous (IV) on days 1-4] and docetaxel (75 mg/m2 IV on days 1 and 8) administered during treatment weeks 1 and 4. All patients received 2-4 cycles of adjuvant chemotherapy of the same dose and drug regimen. Results The use of fluorine-18-fluorodeoxyglucose (18F-FDG) PET/CT significantly reduced the treatment volume delineation of the GTV in 83.3% (20/24) of patients. The 5-year local recurrence-free survival rates of the two groups were 100% and 79.2%, respectively (P = 0.019). The 5-year disease free survival (DFS) rates were 95.8% and 75.0%, respectively (P = 0.018). The 5-year local progression-free survival and DFS rates were significantly different. The 5-year overall survival (OS) rates were 95.8% and 79.2%, respectively. Differences in OS improvement were insignificant (P = 0.079). Late toxicities were similar in the two groups. The most common late toxicities of the two arms were grade 1-2 skin dystrophy, xerostomia, subcutaneous fibrosis, and hearing loss. There were no cases of grade 4 late toxicity. Conclusion The use of 18F-FDG PET/CT-guided dose escalation radiotherapy is well tolerated and can reduce local recurrence rates for patients with locally advanced NPC compared to conventional chemoradiotherapy.