915P - Survival outcomes and toxicity profiles among patients with nonmetastatic nasopharyngeal carcinoma treated with Intensity modulated radiotherapy (IMRT) versus IMRT + Carbon-ion beam radiotherapy (CIRT): A propensity score-matched analysis

Background

To compare survival outcomes and toxic effects among patients with newly diagnosed nonmetastatic nasopharyngeal carcinoma (NPC) when treated with Intensity modulated radiotherapy (IMRT) versus IMRT + carbon-ion radiotherapy (CIRT).

Methods

We performed a retrospective propensity score matching analysis (1:1) of patients treated with IMRT and IMRT + CIRT. Survival was estimated using the Kaplan–Meier method. Multivariate Cox proportional hazards regression analysis was used to identify the independent predictors of survival. We examined the association between risk factors and adverse events (AEs) using Chi-squared tests. AEs analyses were performed using a Cox model and logistic regression.

Results

109 patients who received IMRT + CIRT were included and the median follow-up time was 20.6 months (range: 4.6-82 months). There were no statistically significant differences in locoregional failure–free survival, distant metastasis–free survival, disease-free survival, or overall survival between the two groups, but potentially better in IMRT + CIRT group (P > 0.05, respectively). Nodal boost was the only significant factor associated with LRFS and DFS on multivariable analysis. 37 patients (34.0%) developed grade 3 acute OMs and no grade 4 acute OMs were observed in IMRT + CIRT group. All patients in IMRT + CIRT group developed grade 1 dermatitis. IMRT +CIRT treatment was associated with a significant trend of lower grades of OM and dermatitis (P < 0.05, respectively). Any severe (ie, grade 3) chronic AEs, such as xerostomia, skin fibrosis, temporal lobe necrosis, osteoradionecrosis, or radiation-induced optic neuropathy, was not observed.

Conclusions

IMRT + CIRT for primary nonmetastatic NPC was associated with significantly reduced oral mucositis and dermatitis compared with full course of IMRT, with excellent survival outcomes. Patients with persistent disease after primary treatment and treated with nodal boost had a worse outcome. More accurate assessments of IMRT + CIRT to primary nonmetastatic NPC patients will be imperative.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

The study was funded by the Clinical research on health industry of Shanghai Health Commission (grant numbers: 20214Y0025) The study was funded by the Clinical research of Shanghai Pudong District Health Commission (grant numbers: PW2022A-41).

Disclosure

All authors have declared no conflicts of interest.