Purpose: Pseudoprogression (psPD) is now recognised following radiotherapy with concurrent temozolomide (RT/TMZ) for glioblastoma multiforme (GBM). The aim of this study was to determine the incidence of psPD following RT/TMZ and the effect of psPD on prognosis.
Materials/methods: All patients receiving RT/TMZ for newly diagnosed GBM were identified from a prospective database. Clinical and radiographic data were retrospectively reviewed. Early progression was defined as radiological progression (RECIST criteria) during or within eight weeks of completing RT/TMZ. Pseudoprogression was defined as early progression with subsequent disease stabilization, without salvage therapy, for at least six months from completion of RT/TMZ. The primary outcome was overall survival (Kaplan-Meier) and log rank analysis was used to compare groups.
Results: Out of 111 patients analyzed, 104 were evaluable for radiological response. Median age was 58 years and median follow-up 55 weeks. Early progression was confirmed in 26% and within this group 32% had psPD. Median survival for the whole cohort was 56.7 weeks [95% CI (51.0, 71.3)]. Median survival for patients with psPD was significantly higher than for patients with true early progression (124.9 weeks versus 36.0 weeks, p = 0.0286).
Conclusions: Approximately one third of patients with early progression were found to have psPD which was associated with a favourable prognosis. Maintenance TMZ should not be abandoned on the basis of seemingly discouraging imaging features identified within the first three months after RT/TMZ.