CTNI-13. UPDATES ON CLINICAL OUTCOMES AND TUMOR RECURRENCE PATTERNS OF A HUMAN PILOT STUDY ASSESSING EFFICACY OF BELINOSTAT (PXD-101) COMBINING WITH CHEMORADIATION IN TREATING GLIOBLASTOMA

Glioblastoma (GBM) is highly aggressive with poor prognosis. Belinostat is a histone deacetylase inhibitor with blood–brain barrier permeability that has anti-GBM activity and may enhance effects of chemoradiation. Our institution conducted a clinical trial evaluating clinical efficacy of belinostat with standard-of-care therapy for GBMs.

13 and 14 patients were enrolled into cohort 1 (c1, control) or cohort 2 (c2, belinostat) with 12 in each group with sufficient follow-up MRIs for recurrence analysis. All patients received concurrent, adjuvant temozolomide and focal radiation therapy (RT). For c2 patients, the belinostat regimen (500-750mg/m² 1x/day x 5 days) was given over three cycles every 3 weeks (weeks -1, 2, and 5 of RT). RT margins of 5–10 mm and 3 mm were added to generate clinical tumor volumes and planning target volumes (PTVs). PTV1 (based on FLAIR MRI) and PTV2 (based on CE-T1w MRI) received 51 and 60 Gy, respectively, over 30 fractions. Volume at initial recurrence (rGTV) was contoured.

Mean age was 58.3 years for c1 and 51.1 years for c2. Patient/tumor characteristics were similar between cohorts. Median OS were 16.6 and 18.5 months for c1 and c2 (p=0.538), respectively. Average minimum, maximum and mean radiation dose to rGTV was 54.1 Gy, 64.2 Gy and 62 Gy, for c1, and 47.5 Gy, 57.6 Gy and 53.5 Gy, for c2 (p=0.322, 0.088 and 0.071), respectively. The mean overlap between rGTV and PTV1/PTV2 for c1 & c2 were 99.2% & 96.9%/99.8% & 78.7% (p=0.489/0.133), respectively.

Median OS was slightly longer for c2 though not statistically significant. rGTV in c1 received higher radiation doses and had more overlap with PTV2 than in c2. Out-of-field recurrence appears more likely in c2 suggesting better infield control with belinostat. This study highlights the potential of belinostat as a synergistic therapeutic agent for GBM treatment.