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Int J Radiat Oncol Biol Phys. 2018 May 1;101(1):226-233. doi: 10.1016/j.ijrobp.2018.01.060. Epub 2018 Feb 2.

Long-Term Outcomes and Prognostic Factors After Pencil-Beam Scanning Proton Radiation Therapy for Spinal Chordomas: A Large, Single-Institution Cohort.

Author information

1
Department of Radiation Oncology, University of Maryland Medical Center, Baltimore, Maryland; Center for Proton Therapy, Paul Scherrer Institute, Villigen, Switzerland.
2
Center for Proton Therapy, Paul Scherrer Institute, Villigen, Switzerland.
3
Center for Proton Therapy, Paul Scherrer Institute, Villigen, Switzerland; Radiotherapeutisch Instituut Friesland, Leeuwarden, The Netherlands.
4
Center for Proton Therapy, Paul Scherrer Institute, Villigen, Switzerland; Universitätsklinik für Radio-Onkologie, Inselspital Universitatsspital Bern, Bern, Switzerland.
5
Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, Maryland.
6
Center for Proton Therapy, Paul Scherrer Institute, Villigen, Switzerland; University of Bern, Bern, Switzerland; University of Zürich, Zürich, Switzerland. Electronic address: damien.weber@psi.ch.

Abstract

PURPOSE:

To evaluate the efficacy and safety of high-dose pencil-beam scanning proton therapy (PBS-PT) in the adjuvant treatment of spinal chordomas.

METHODS AND MATERIALS:

Between 1997 and 2015, 100 patients with spinal chordomas (median age, 56 years; range, 25-81 years) were treated with adjuvant PBS-PT at the Paul Scherrer Institute: 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 radiation therapy dose prescribed was 74 Gy (relative biological effectiveness [RBE]) (range, 59.4-77 Gy [RBE]). Thirty-nine patients (39%) had undergone surgical stabilization, primarily with titanium hardware, before radiation therapy.

RESULTS:

With a median follow-up of 65 months (range, 13-175 months), 5-year local control, disease control, and overall survival rates were 63% (95% confidence interval [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 surgical stabilization 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.

CONCLUSION:

For spinal chordomas, PBS-PT remains a highly effective and safe method for delivery of dose-escalated adjuvant radiation therapy. The presence of metallic surgical stabilization prognosticates for worsened outcomes. Further investigation is warranted to characterize ideal treatment volumes and effect of surgical stabilization on therapy for these challenging tumors.

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