Yes and no. Yes, they did have choice. But none of them pick the avastin alone. It sounds like the first 22 patients were given avastin alone. Then, the remaining 24 were given a choice. This was not random, but it was also not a selection process to pick the healthiest patients for VB111.
Here are the details from 20-F (as a rule, SEC filings are much more detailed than news releases):
In order to explore the efficacy of the combination regimen, in March 2015 we performed a current interim analysis which compared patients who received bevacizumab alone after progression on VB-111 monotherapy, in a “sequential regimen”, to those who after progression on VB-111 monotherapy received bevacizumab combined with continued VB-111, termed “combination regimen”.
As of March 24, 2015, our interim Phase 2 data include 46 patients with rGBM. VB-111 monotherapy was discontinued upon progression in 22 patients who were then treated with bevacizumab alone. The remaining 24 patients, upon disease progression on VB-111 monotherapy, could elect to receive further treatment with VB-111 in combination with bevacizumab. Twenty three have received combined therapy; one patient remains stable on VB-111 monotherapy at 424 days. VB-111 in combination with bevacizumab demonstrated a statistically significant improvement in overall survival, with median overall survival of 414 days, compared to 235 days in patients on VB-111 followed by bevacizumab alone (p=0.05). Although these data are not fully mature, they are statistically significant.
