A prospective clinical trial of proton therapy for chordoma and chondrosarcoma: Feasibility assessment.

Background/objectives: Proton therapy (PRT) has emerged as a treatment option for chordomas/chondrosarcomas to escalate radiation dose more safely. We report results of a phase I/II trial of PRT in patients with chordoma/chondrosarcoma.

Methods: Twenty adult patients with pathologically confirmed, nonmetastatic chordoma or chondrosarcoma were enrolled in a single-institution prospective trial of PRT from 2010 to 2014. Seventeen patients received adjuvant PRT and three received definitive PRT. Median dose was 73.8 Gy(RBE; range 68.4-79.2 Gy) using PRT-only (n = 6) or combination PRT/intensity-modulated radiotherapy (IMRT) (n = 14). Quality-of-life (QOL) and fatigue were assessed weekly and every 3 months posttreatment with the Functional Assessment of Cancer Therapy - Brain (FACTBr) and Brief Fatigue Inventory. Primary endpoint was feasibility (90% completing treatment with < 10 day treatment delay and ≤ 20% unexpected acute grade ≥ 3 toxicity).

Results: Tumors included chordomas of the skull base (n = 10), sacrum (n = 5), and cervical spine (n = 3), and skull base chondrosarcomas (n = 2). Median age was 57. The 80% had positive margins/gross disease. Median follow-up was 37 months. Feasibility endpoints were met. The 3-year local control and progression-free survival was 86% and 81%. There were no deaths. Two patients had acute grade 3 toxicity (both fatigue). One had late grade 3 toxicity (epistaxis and osteoradionecrosis). There were no significant differences in patient reported fatigue or QOL from baseline to the end-of-treatment.

Conclusions: We report favorable local control, survival, and toxicity following PRT.