EGFR and glycogen storage disease VI: Multivariable analysis suggested that an EGFR mutation (HR: 0.50, 95 % CI: 0.30–0.82), age (HR: 1.03, 95 % CI: 1.00–1.05), and active extra-cranial disease (HR: 3.30, 95 % CI: 1.70–6.41) were independently associated with survival.