Work

Nimg-35results of Exploratory 18f-flt Pet Imaging in Ten Recurrent High-grade Glioma Patients Treated With the Selective T-type Calcium Channel Blocker Mibefradil Followed by Temozolomide (abtc Trial 1101)

Year: 2015

Type: article

Abstract: BACKGROUND: Mibefradil (MIB) is a selective T-type calcium channel blocker that has shown preclinical impact on cell cycle activity, specifically arrest at G1/S in tumor cells, suggesting a potential chemo-sensitizing effect if given prior to chemotherapy. In our study, MIB was administered orally QID x 7 days prior to standard temozolomide (150-200 mg/m2 x 5/28d) in recurrent high-grade glioma (HGG) patients. 18F-FLT PET was used as an exploratory imaging biomarker to assess influence of MIB on overall tracer accumulation in tumor. METHODS: 18F-FLT PET was performed in 10 patients treated at the maximum tolerated dose of MIB (87.5 mg po QID) at 5 different institutions. Prior to MIB administration, 2 PET scans were performed as a double baseline to assess repeatability of PET measurements. A third scan was performed on day 7 of MIB treatment to assess 18F-FLT uptake for response. Tumor standardized uptake values (SUVs) were measured at a central laboratory by automatically positioning a 1mL sphere at the region of highest uptake (SUVpeak). RESULTS: The double baseline data indicated 95% limits of repeatability of 18.5% (6.7% within-patient coefficient of variation) for SUVpeak. Two of the 10 patients demonstrated a drop in SUVpeak after 7 days of MIB that exceeded these limits (-47% and -67%). No significant change between double baseline and day 7 of MIB was seen in the remaining 8 patients. CONCLUSIONS: In this first 18F-FLT PET imaging study within a multicenter HGG trial, 18F-FLT PET was found to be feasible and highly repeatable. The results suggest influence of MIB on tumor accumulation of the radiotracer, possibly in part due to alterations in cell cycle activity in a subset of patients, but the precise mechanism remains to be determined as tracer delivery/transport effects may also be contributing to the decline in signal observed in the two patients.

Source: Neuro-Oncology

DOI: 10.1093/neuonc/nov225.35