Abstract
This phase II randomized controlled trial aimed at comparing the efficacy and toxicity of diffusion-weighted magnetic resonance imaging (DWI)-guided dose painting radiotherapy (DP-RT), FDG-PET/CT-guided DP-RT, and conventional MRI-based radiotherapy (RT) in locoregionally advanced nasopharyngeal carcinoma (NPC). A total of 330 patients with stage III-IVa NPC disease were randomly assigned in a 1:1:1 ratio to receive induction chemotherapy followed by concurrent chemoradiotherapy by DWI-guided DP-RT (group A, n = 110), FDG-PET/CT-guided DP-RT (group B, n = 110), or conventional MRI-based RT (group C, n = 110). All patients received volumetric modulated arc therapy (VMAT). In group A, subvolume GTVnx-DWI (gross tumor volume of nasopharynx in DWI) was defined as the areas within the GTVnx (gross tumor volume of nasopharynx) with an apparent diffusion coefficient (ADC) below the mean ADC (ADC < mean). In group B, subvolume GTVnx-PET (gross tumor volume of nasopharynx in PET images) was defined within GTVnx as the SUV50%max isocontour. The doses to GTVnx-DWI in group A and GTVnx-PET in group B were escalated to 75.2 Gy/32 fx in patients with T1-2 disease and to 77.55 Gy/33 fx in those with T3-4 disease in 2.35 Gy per fraction. In group C, planning gross tumor volume of nasopharynx (PGTVnx) was irradiated at 70.4 to 72.6 Gy/32 to 33 fx in 2.2 Gy per fraction. This trial is registered with chictr.org.cn (ChiCTR2200057476). Group A and B showed significant higher complete response (CR) rates than group C (100%, 100%, and 96.4% for group A, B and C, respectively, p = 0.036). In groups A, B and C, the 1-year local recurrence-free survival (LRFS) rates were 100%, 100%, and 94.5%, respectively (p = 0.002). The 1-year disease-free survival (DFS) rates were 100%, 99.1%, and 92.7%, respectively (p = 0.001). The 1-year distant metastasis-free survival (DMFS) rates were 100%, 99.1%, and 93.6%, respectively (p = 0.004). The 1-year overall survival (OS) rates were 100%, 100%, and 95.4%, respectively (p = 0.006). Group A and B had significantly higher 1-year LRFS, DFS, DMFS, and OS than those in group C. No significant differences were observed in LRFS, DFS, DMFS and OS between group A and B. Group B (PET/CT group) had a higher incidence of grade 3-4 acute ototoxicity (3.6%) than group A (0%) and group C (0%, p = 0.036). No significant differences in other grade 3-4 acute adverse events and late toxic effects were observed among the three groups, and no patient had grade 5 toxicities. Multivariate analysis showed that dose painting (DWI-guided DP-RT and PET/CT-guided DP-RT vs conventional MRI-based RT) was associated with improved LRFS, DFS, DMFS and OS. Both DWI-guided DP-RT and PET/CT-guided DP-RT plus chemotherapy are associated with improved LRFS, DFS, DMFS and OS compared with conventional MRI-based RT among patients with locoregionally advanced NPC. DWI-guided DP-RT does not increase toxicities, but PET/CT-guided DP-RT has higher incidence of acute ototoxicity.
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