Impact of upgraded radiotherapy system on outcomes in postoperative head and neck squamous cell carcinoma patients

BACKGROUND: This study was performed to evaluate the impact of upgrade of radiotherapy system, including launch of intensity-modulated radiation therapy (IMRT), on the therapeutic outcomes. MATERIALS AND METHODS: Patients with head and neck (H&N) squamous cell carcinoma (SCC) who underwent postoperative radiotherapy at our hospital between June 2009 and July 2019 were retrospectively reviewed. In July 2014, we converted the radiotherapy technique for these patients from a 3-dimensional conformal radiotherapy (3D-CRT) to IMRT, along with the adoption of a meticulous planning policy and a few advanced procedures, including online imaging guidance. RESULTS: A total of 136 patients (57 treated with the previous system and 79 treated with the upgraded system) were reviewed. There were significantly more patients with extracapsular extension in the upgraded-system group than the previous-system group (p = 0.0021). There were significantly fewer patients with ≥ Grade 2 acute and late adverse events in the upgraded-system group than the previous-system group. The differences in progression-free survival (PFS), distant metastasis-free survival (DFFS), locoregional progression-free survival (LRPFS), and overall survival (OS) between the two groups were not statistically significant (p = 0.8962, 0.9926, 0.6244, and 0.4827, respectively). Multivariate analysis revealed that the upgrade had neither positive nor negative impact on survival outcomes. Extracapsular extension was independently associated with decreased LRPFS and OS (p = 0.0499 and 0.0392, respectively). CONCLUSIONS: The IMRT-centered upgrade was beneficial for the postoperative patients with H&N SCC, because survival outcomes were sustained with less toxicities.