Use of Cox regression with treatment status as a time‐dependent covariate to re‐analyze survival benefit excludes immortal time bias effect in patients with glioblastoma who received prolonged adjuvant treatment with valganciclovir. Issue 1 (6th January 2014) - Söderberg‐Naucler, Cecilia; Peredo, Inti; Rahbar, Afsar; Hansson, Fredrik; Nordlund, Anders; Stragliotto, Giuseppe