Comparison of Tumor Control After Stereotactic Radiosurgery or Pencil Beam Proton Therapy for Newly Diagnosed Clival Chordomas: A Single-Center Retrospective Study

Objective: To compare outcomes of proton radiation therapy (PRT), stereotactic radiosurgery (SRS), and x-ray-based radiation with an SRS boost (XRT + SRS) for newly diagnosed clival chordoma. Methods: Consecutive patients who underwent PRT or SRS in our facility were retrospectively reviewed. Results: A total of 59 patients were identified (PRT, 36; SRS, 11; XRT + SRS, 12). The mean age (± standard deviation) was 46 ± 20 years, with 54% being male. The mean tumor diameter (± standard deviation) was 3.7 ± 1.5 cm, and 21 (36%) involved the lower clivus. Gross total or near-total resection was attained in 27 patients (46%), all of whom received PRT. PRT was administered with a median prescribed dose of 70.8 Gy (range, 66.0–76.0). SRS involved a median marginal dose of 16 Gy (range, 14–20) and a median maximal dose of 36 Gy (range, 30–45). The XRT + SRS group was treated with an SRS marginal dose of 12.5 Gy (range, 10–20), a maximal dose of 27 Gy (range, 20–40), and an XRT prescription dose of 50.4 Gy (range, 45.0–59.4). Fifteen recurrences were observed (PRT, 6; SRS, 5; XRT + SRS, 4). For the entire cohort (n = 59), recurrence was associated with the degree of resection (P = 0.042), but not with radiation groups (P = 0.98). For patients after subtotal resection or biopsy (n = 32), the SRS ± XRT group was associated with few recurrences (hazard ratio, 0.260; 95% confidence interval, 0.069–0.98; P = 0.046). Conclusions: Patients after subtotal resection or biopsy may benefit from the incorporation of SRS.