Group 2- Recurrent GBM; bevacizumab refractory [defined as having progressed (grown through) by RANO criteria within two months of prior bevacizumab treatment]

Results are available for all 25 patients enrolled in this arm. One patient continues to receive treatment and 6 continue to be followed for survival.  
ReACT Overall Survival and Progression-free Survival Bevacizumab-Refractory Recurrent GBM
  Median, months 95% CI
OS 5.6 (3.2, 6.7)
PFS 1.9 months (1.8, 2.8)

PFS results in this refractory population may be more consistent with the profile of an immunotherapy candidate where PFS does not always correlate directly with an overall survival benefit. The median OS of 5.6 months is noteworthy in these heavily pretreated, refractory EGFRvIII-positive patients. A review of the literature assessing survival in recurrent patients who are bevacizumab experienced across eight independent studies suggests a weighted-average survival of 3.6 months (range of 2.6 to 5.8 months) in all-comers. It is important to note that these eight studies do not necessarily meet the strict definition of refractory applied in the ReACT study and that these studies included EGFRvIII-negative patients who tend to perform better.

Again, results suggest that early development of high anti-EGFRvIII titer may be predictive for improved outcome in this patient population as improved survival was associated with rapid generation of a robust humoral response. For the 13 patients with high titers by day 57, median OS was 6.6 months versus 3.2 months for the 11 patients who did not develop high titers (HR = .33 (0.08, 0.67); p=0.009). 69% of patients with high titers were alive at 6 months compared to 18% of patients who did not develop high titers. With no comparative data available to define expected outcome for EGFRvIII-positive patients who have failed bevacizumab, an ambitious goal of progression-free survival of 20% at 6 months was established as the primary endpoint for this arm; 2 out of 25 (8%) patients are progression-free at six months.

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