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

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.

The effect of hormonal treatment on conspicuity of prostate cancer: implications for focal boosting radiotherapy.

BACKGROUND AND PURPOSE: For focal boosting of prostate tumors, three questions are important regarding the use of hormonal therapy. Does prolonged hormonal treatment affect the conspicuity of tumor tissue on diffusion weighted imaging (DWI) and dynamic contrast-enhanced (DCE-MRI) images? Is tumor delineation possible in patients using hormonal treatment? Can we identify specific imaging thresholds for tumor delineation in patients after prolonged androgen deprivation? MATERIALS AND METHODS: Ninety-six patients were included. Using multivariate linear regression analyses, we investigated if DWI and DCE-MRI parameter maps are different in patients receiving hormonal treatment for 0-3 or >3 months. Furthermore, logistic regression was performed to obtain specific imaging thresholds for tumor tissue for the two patient groups. RESULTS: We found a significantly higher diffusion and lower perfusion of tumor tissue in the >3 months hormonal treatment group compared to the 0-3 group. This resulted in lower tumor conspicuity. Nevertheless, in 18/21 of the patients in the >3 months treatment group, a suspicious lesion could be defined based on the MR images. Based on logistic regression, different imaging thresholds should be set for tumor detection in the two treatment groups. CONCLUSIONS: Prolonged androgen deprivation decreases tumor conspicuity. Different imaging thresholds need to be set to delineate tumor in patients who have had prolonged hormonal treatment.