Magnetic resonance imaging signal characteristics associated with prognosis of skull base chordoma after gamma knife radiosurgery

Objective To investigate the association between the magnetic resonance imaging (MRI) signal characteristics of skull base chordoma and radiosurgical outcomes. Methods Twenty-four patients with skull base chordomas treated with Gamma Knife radiosurgery (GKRS) after previous surgical resection were retrospectively (2001–2021) examined. Pre-GKRS MRIs were analyzed for R T2 (tumor-to-brainstem signal intensity ratio on T2-weighted imaging), R CE (tumor-to-brainstem signal intensity ratio on contrast-enhanced T1-weighted imaging), and mean apparent diffusion coefficient (ADC). Correlations of the parameters with patient survival and local tumor progression were made by using Cox regression and Kaplan–Meier analyses. Results During a median follow-up of 46 months after GKRS, 9 patients died with significantly more local tumor progression events (median number: 2 vs 0, P = .012) than did 15 alive patients. On multivariable analysis, higher mean ADC was associated with longer patient survival ( P = .016) after GKRS. The actuarial 5-year overall survival rates were 88.9% versus 54.7% for chordomas with an ADC of ≥ 1270 × 10 –6 mm 2 /s versus