Comparative effectiveness of Volumetric Modulated Arc Therapy versus tomotherapy in locally advanced nasopharyngeal carcinoma: a propensity score-matched retrospective cohort study.
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BACKGROUND: Nasopharyngeal carcinoma (NPC) remains a major healthcare burden in endemic regions, and locally advanced disease demands optimal radiotherapy for curative intent. Although both Volumetric Modulated Arc Therapy (VMAT) and tomotherapy (TOMO) are both advanced conformal radiotherapy techniques, their comparative efficacy in locally advanced NPC has not been fully clarified by large-scale studies that adequately control for selection bias. This study compared the therapeutic efficacy and safety of VMAT versus TOMO in patients with locally advanced NPC. METHODS: We performed a retrospective cohort study of 1,974 patients with histologically confirmed locally advanced NPC treated at our institution between January 2016 and December 2019. Patients received either VMAT (n = 1,720) or TOMO (n = 254) combined with systemic therapy per institutional protocols. To reduce selection bias, propensity score matching (PSM) was conducted at a 1:1 ratio using nearest-neighbor matching without replacement, with a 0.2 standard deviation caliper to balance baseline characteristics between groups. Primary endpoints included overall survival (OS), progression-free survival (PFS), locoregional recurrence-free survival (LRFS), and distant metastasis-free survival (DMFS). The secondary endpoints were treatment response rates and treatment-related adverse events. RESULTS: After PSM, 979 patients were included in the final analysis (728 VMAT and 251 TOMO). Standardized mean differences (SMDs) for all baseline variables were < 0.1, confirming adequate balance between groups. With a median follow-up of 42 months, no significant differences in the 3-year survival rates were observed between the VMAT and TOMO groups: OS (85.2% vs. 87.1%, P = 0.645), PFS (78.9% vs. 81.2%,P = 0.391), LRFS (91.3% vs. 93.1%, P = 0.505), and DMFS (85.7% vs. 87.4%, P = 0.383). Both techniques achieved high overall response rates (ORR) (96.7% vs. 97.6%, p = 0.418). For safety, xerostomia occurred significantly less frequently in the TOMO group (33.86% vs. 46.84%, p < 0.001), consistent with its superior ability to spare parotid glands, while other adverse events showed no significant intergroup differences. CONCLUSIONS: VMAT and TOMO yield comparable therapeutic efficacies in patients with locally advanced NPC. Both advanced radiotherapy techniques are effective options in multimodality care. The choice between them should be based on institutional capacity and patient-specific factors, including quality-of-life needs and target volume anatomy, rather than anticipated survival benefits.