ESTRO 2023 - Abstract Book

S991

Digital Posters

ESTRO 2023

Conclusion Most eligible outcome prediction models contained methodological issues, introducing a high risk of bias, which may affect accuracy in heterogeneous populations. Inadequate reporting of complete model information was also demonstrated. Careful critical appraisal of outcome prediction model publications should be undertaken before clinical use. It is also recommended that future prediction model studies use the TRIPOD reporting guidelines to ensure that sufficient information is provided to allow for critical appraisal and independent external validation. Independent external validation studies in the local population and demonstration of clinical impact are essential for the clinical implementation of outcome prediction models.

PO-1237 Efficacy and tolerance of stereotactic re-irradiation in the treatment of head and neck cancers

X. Liem 1 , C. Delerue 1 , E. Bogart 2 , X. Mirabel 1 , S. Lals 1 , M. Barthoulot 2 , J. Laffarguette 3 , E. Lartigau 1 , D. Pasquier 1

1 Oscar-Lambret Center, Radiotherapy, Lille, France; 2 Oscar-Lambret Center, Clinical Research and Innovation, Lille, France; 3 Oscar-Lambret Center, Medical Physics, Lille, France Purpose or Objective Stereotactic radiotherapy potentially treats unresectable recurrences of previously irradiated head and neck (H&N) cancer. This study aimed to evaluate its efficacy and tolerance. Materials and Methods This observational, retrospective, monocentric study investigated patients who had undergone 36-Gy, six-fraction stereotactic re-irradiation (CyberKnife®) for recurrent/secondary H&N cancer between 2007 and 2019 at the Oscar Lambret Center. Patient characteristics and toxicities were assessed. Overall survival (OS) was estimated using the Kaplan–Meier method. OS and toxicity prognostic factors were determined using a Cox model. Results 110 patients were included from analysis, treated between January 2007 and December 2020. The median follow-up time was 106.3 months. The 2-year OS rate was 43.8% (95% confidence interval: 34.3–52.9; median survival: 20.8 months [16.5– 26.3]). The cumulative 2-year local-recurrence, regional-recurrence, and distant-metastasis rates were 52.2% (42.4–61.1%), 12.8% (7.4–19.8%), and 11% (6.0–17.6%), respectively. In the multivariate analysis, performance status (HR[PS1]=2.05[1.19– 3.56]; HR[PS2–3]=5.31[2.47–11.4], p<0.001), and planning target volume (HR=1.07[1.00–1.13], p=0.037) were significantly associated with mortality risk. 73 patients received concomitant cetuximab, and it was not significantly beneficial (HR=1.34[0.80–2.26], p=0.26). Forty six patients had grade 3+ acute toxicity and 42 grade 3+ late toxicity. Two grade 4 bleeds and no treatment-related deaths were reported.