Diffusion-Weighted Magnetic Resonance Imaging-Guided Dose Painting in Patients With Locoregionally Advanced Nasopharyngeal Carcinoma Treated With Induction Chemotherapy Plus Concurrent Chemoradiotherapy: A Randomized, Controlled Clinical Trial

Abstract

We hypothesized that diffusion-weighted magnetic resonance imaging (DWI)-guided dose-painting intensity modulated radiation therapy (DP-IMRT) is associated with improved local tumor control and survival in locoregionally advanced nasopharyngeal carcinoma (NPC). The purpose of this randomized study was to compare the efficacy and toxicity of DWI-guided DP-IMRT to conventional magnetic resonance imaging (MRI)-based IMRT in locoregional advanced NPC. A total of 260 patients with stage III-IVa NPC disease were randomly assigned in a 1:1 ratio to receive induction chemotherapy followed by chemoradiotherapy by DWI-guided DP-IMRT (group A, n=130) or conventional MRI-based IMRT (group B, n=130) in this prospective clinical trial. 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) according to MRI before induction chemotherapy. The dose to GTVnx-DWI was 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 B, planning gross tumor volumeof nasopharynx 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 (ChiCTR1800015779). A total of 260 patients were included in the trial (130 patients in group A and 130 in group B). Complete response rates after chemoradiotherapy were 99.2% (129 of 130) and 93.8% (122 of 130) in groups A and B, respectively (P=.042). At a median follow-up of 25 months, DWI-guided DP-IMRT was associated with improved 2-year disease-free survival (DFS; 93.6% [95% confidence interval {CI}, 88.1%-99.1%] vs 87.5% [95% CI, 81.4%-93.6%], P=.015), local recurrence-free survival (100% [95% CI, not applicable {NA}] vs 91.3% [95% CI, 85.4%-97.2%]), locoregional recurrence-free survival (LRRFS; 95.8% [95% CI, NA] vs 91.3% [95% CI, 85.4%-97.2%]), distant metastasis-free survival (DMFS; 97.8% [95% CI, NA] vs 90.9% [95% CI, 85.8%-96.0%]), and overall survival (100% [95% CI, NA] vs 94.5% [95% CI, 89.2%-99.8%]). Zero and 3 patients had local-only recurrences in group A and B, respectively. The most common site of first failure in each arm was distant organ failure. No statistically significant differences in acute and late toxic effects were observed. Multivariate analyses showed that DP (DWI-guided DP-IMRT vs conventional MRI-based IMRT without DP) was associated with DFS, local recurrence-free survival, LRRFS, and distant metastasis-free survival. Epstein-Barr virus DNA level was associated with DFS and LRRFS. DWI-guided DP-IMRT plus chemotherapy is associated with a disease-free survival benefit compared with conventional MRI-based IMRT among patients with locoregionally advanced NPC without increasing acute toxic effects.