Long-Term Outcomes and Prognostic Factors Following Pencil-Beam Scanning Proton Radiotherapy for Spinal Chordomas: A Large, Single-Institution Cohort

Publication date: Available online 2 February 2018
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): J.W. Snider, Ralf A. Schneider, Davey Poelma-Tap, Sonja Stieb, Fritz R. Murray, Lorenzo Placidi, Francesca Albertini, Antony Lomax, Alessandra Bolsi, Ulrike Kliebsch, Robert Malyapa, Damien C. Weber
PurposeTo evaluate the efficacy and safety of high-dose pencil-beam scanning proton therapy (PBS-PT) in the adjuvant treatment of spinal chordomas.Methods and MaterialsBetween 1997 and 2015, 100 patients with spinal chordomas (median age, 56 years; range, 25–81 years) were treated with adjuvant PBS-PT at the XXXX: cervical (n=46), thoracic (n=4), lumbar (n=12), and sacral (n=38). The majority (88%) received PBS-PT alone rather than combined photon–proton therapy. The median radiotherapy dose prescribed was 74 Gy(RBE) (range, 59.4–77 Gy[RBE]). Thirty-nine (39%) patients had undergone surgical stabilization (SS), primarily with titanium hardware, prior to radiotherapy.ResultsWith a median follow-up of 65 months (range, 13–175 months), 5-year local control, disease control, and overall survival rates were 63% (95%CI: 57.7–68.7%; median, 103 months), 57% (95%CI: 50.9-62.1%; median, 82 months), and 81% (95%CI: 76.8-85.6%; median, 157 months), respectively. On univariate and multivariate analyses, the presence of SS was highly prognostic for worsened outcomes. Multivariate analysis also revealed the extent of treatment volumes and presence of gross residual disease to be important in predicting outcomes. High-grade (≥grade 3) toxicities were rare in both the acute (8%) and late (6%) settings.ConclusionFor spinal chordomas, PBS-PT remains a highly effective and safe method for delivery of dose-escalated adjuvant radiotherapy. The presence of metallic SS prognosticates for worsened outcomes. Further investigation is warranted to characterize ideal treatment volumes and effect of SS on therapy for these challenging tumors.



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