Proton therapy for skull-base chondrosarcoma, a single-institution outcomes study.

Background: We sought to evaluate the effectiveness of definitive or adjuvant external-beam proton therapy on local control and survival in patients with skull-base chondrosarcoma.

Methods: We reviewed the medical records of 43 patients with a median age of 49 years (range, 23-80 years) treated with double-scattered 3D conformal proton therapy for skull-base chondrosarcomas between January 2007 and February 2016. Proton therapy-related toxicities were scored using CTCAE v4.0.

Results: The median radiotherapy dose was 73.8 Gy(RBE) (range, 64.5-74.4 Gy[RBE]). Thirty-six (84%) and 7 (16%) patients underwent surgical resection or biopsy alone. Tumor grade distribution included: grade 1, 19 (44%) patients; grade 2, 22 (51%); and grade 3, 2 (5%). Forty patients had gross disease at the time of radiotherapy and 7 patients were treated for locally recurrent disease following surgery. The median follow-up was 3.7 years (range, 0.7-10.1 years). There were no acute grade 3 toxicities related to RT. At 4 years following RT, actuarial rates of overall survival, cause-specific survival, local control, and RT-related grade 3 toxicity-free survival were 95%, 100%, 89%, and 95%.

Conclusion: High-dose, double-scattered 3D conformal proton therapy alone or following surgical resection for skull-base chondrosarcoma is an effective treatment with a high rate of local control with no acute grade 3 radiation-related toxicity. Further follow-up of this cohort is necessary to better characterize long-term disease control and late toxicities.