Journal Article

Long-term outcomes and prognostic factors of skull-base chondrosarcoma patients treated with pencil-beam scanning proton therapy at the Paul Scherrer Institute

Damien C. Weber, Shahed Badiyan, Robert Malyapa, Francesca Albertini, Alessandra Bolsi, Antony J. Lomax and Ralf Schneider

in Neuro-Oncology

Volume 18, issue 2, pages 236-243
Published in print February 2016 | ISSN: 1522-8517
Published online August 2015 | e-ISSN: 1523-5866 | DOI: http://dx.doi.org/10.1093/neuonc/nov154
Long-term outcomes and prognostic factors of skull-base chondrosarcoma patients treated with pencil-beam scanning proton therapy at the Paul Scherrer Institute

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Background

Skull-base chondrosarcoma (ChSa) is a rare disease, and the prognostication of this disease entity is ill defined.

Methods

We assessed the long-term local control (LC) results, overall survival (OS), and prognostic factors of skull-base ChSa patients treated with pencil beam scanning proton therapy (PBS PT). Seventy-seven (male, 35; 46%) patients with histologically confirmed ChSa were treated at the Paul Scherrer Institute. Median age was 38.9 years (range, 10.2–70.0y). Median delivered dose was 70.0 GyRBE (range, 64.0–76.0 GyRBE). LC, OS, and toxicity-free survival (TFS) rates were calculated using the Kaplan Meier method.

Results

After a mean follow-up of 69.2 months (range, 4.6–190.8 mo), 6 local (7.8%) failures were observed, 2 of which were late failures. Five (6.5%) patients died. The actuarial 8-year LC and OS were 89.7% and 93.5%, respectively. Tumor volume > 25 cm3 (P = .02), brainstem/optic apparatus compression at the time of PT (P = .04) and age >30 years (P = .08) were associated with lower rates of LC. High-grade (≥3) radiation-induced toxicity was observed in 6 (7.8%) patients. The 8-year high-grade TFS was 90.8%. A higher rate of high-grade toxicity was observed for older patients (P = .073), those with larger tumor volume (P = .069), and those treated with 5 weekly fractions (P = .069).

Conclusions

This is the largest PT series reporting the outcome of patients with low-grade ChSa of the skull base treated with PBS only. Our data indicate that protons are both safe and effective. Tumor volume, brainstem/optic apparatus compression, and age were prognosticators of local failures.

Keywords: chondrosarcoma; pencil beam scanning; prognostic factors; proton therapy; skull-base tumors

Journal Article.  5440 words.  Illustrated.

Subjects: Medical Oncology ; Neurology

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