Impact of the Radiotherapy Delay After Surgery on Progression-Free Survival in Newly Diagnosed Skull-Base Chordoma: A Monocentric Retrospective Series

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Introduction: Maximal resection combined with postoperative radiotherapy (RT) has been the standard strategy to reduce the risk of recurrence in skull base chordoma (SBC). However, the impact of the timing of proton beam therapy initiation after surgery on patient outcomes remains unclear and has not yet been systematically studied. This study aimed to evaluate the effect of RT delay on progression-free survival (PFS) in newly diagnosed SBC patients. Methods: A retrospective analysis was conducted on patients who underwent surgery followed by RT at our institution between February 1991 and July 2024. Exclusion criteria included prior RT and/or surgery, adjuvant RT not involving proton beam therapy, tumor recurrence before RT, pediatric cases (<18 years), insufficient follow-up, and missing RT data. Patients were stratified into two groups according to RT initiation time: <3.9 months (low RT delay) and ≥3.9 months (high RT delay). Kaplan–Meier survival curves and Cox regression models were used to assess PFS. Results: Ninety-six patients were analyzed. The mean follow-up was 67.1 ± 42.6 months. At last follow-up, 26 patients (27.1%) had experienced tumor recurrence. The 5- and 10-year PFS rates were 72.1% and 59.5%, respectively. The two groups were generally comparable, except that the high RT delay group had a higher proportion of intradural tumors and a lower rate of GTR. In both univariate and multivariate analyses, RT delay was not significantly associated with PFS ( p = 0.27 and p = 0.56, respectively). Independent prognostic factors for shorter PFS included no GTR ( p = 0.02) and K i -67 LI ≥6% ( p = 0.03). Conclusion: This study demonstrates that an RT delay of ≥3.9 months after surgery does not significantly impact PFS in patients with newly diagnosed SBC. Rather than representing a drawback, this interval may provide a valuable window to refine risk stratification, particularly through multiomic biomarkers, and to better guide the indication for RT in selected patients. Publication History Article published online: 27 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany

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