Normal tissue complication probability model of temporal lobe injury following re-irradiation of CIRT for local recurrent nasopharyngeal carcinoma.

Authors

Xiyin Guan, Jiayao Sun, Jiyou Peng, Xing Xing, Chaosu Hu

Published in

Frontiers in oncology. Volume 16. Pages 1853143. Epub Jun 26, 2026.

Abstract

Temporal lobe injury (TLI) is a significant complication after carbon-ion re-irradiation (reRT-CIRT) for locally recurrent nasopharyngeal carcinoma (rNPC). This study established normal tissue complication probability (NTCP) models for TLI based on (1) the second-course CIRT dose alone and (2) the cumulative dose of both radiotherapy courses, with the goal of defining clinically applicable, modality-specific dose constraints.
Eighty-nine rNPC patients who underwent reRT-CIRT between 2016 and 2020 were retrospectively analyzed. Deformable image registration transferred initial IMRT dose distributions onto CIRT planning scans, and voxel-wise cumulative equivalent doses in 2-Gy fractions (EQD₂, α/β = 3 Gy) were calculated. Patients were stratified into training (n = 52) and validation (n = 37) cohorts. Multivariate logistic regression identified TLI predictors under two scenarios-second-course dose only versus cumulative two-course dose-and model performance was evaluated by ROC analysis.
TLI occurred in 27 patients (30.3%), predominantly unilateral (24/27); 14 were Grade 1 (asymptomatic, MRI-detected only), 7 Grade 2, 5 Grade 3, and 1 Grade 4. The second-course D_0.5cc model [TD₅ 34.27 Gy (RBE); TD₅₀ 78.53 Gy (RBE); AUC 0.8450, 95% CI 0.7571-0.9329] and the cumulative D₅cc model (TD₅ 41.60 Gy; TD₅₀ 124.31 Gy; AUC 0.8225, 95% CI 0.7228-0.9222) yielded equivalent and concordant risk stratification, with the inter-group dose difference primarily driven by the re-irradiation course. Compared with our previous photon-based reRT model, the CIRT-derived TD₅₀ for D_0.5cc and D₁cc were ~20% higher (78.5 vs. 65.4 Gy; 76.8 vs. 62.9 Gy), indicating that photon-based constraints systematically overestimate TLI risk under CIRT.
A CIRT-specific NTCP model based on the second-course D_0.5cc achieves predictive performance equivalent to cumulative two-course dose summation, obviating prior-course dose reconstruction. This simplified, modality-specific tool offers practical guidance for individualized risk assessment and dose-constraint optimization in carbon-ion re-irradiation for rNPC.

PMID:
42434735
Bibliographic data and abstract were imported from PubMed on 11 Jul 2026.

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