P17.02.b correlations between clinical benefit to second line regimens and nadh-flim-based drug response assessment model on recurrent gbm patient-derived organoids

Abstract OBJECTIVE To investigate the ex-vivo/in-vivo correlation between clinical benefit to second line chemotherapy regimens in patients with recurrent glioblastoma (GBM) who underwent second surgery and NADH-FLIM-based drug response assessment on the related recurrent GBM patient-derived organoids. MATERIAL AND METHODS We enrolled five adult patients affected by GBM IDH wild-type after surgery for recurrent glioblastoma. In-vitro 3D glioblastoma organoids (GBM-EXPs) were derived from patients’ resected tumors. After 3 days from culture, organoids were treated with chemotherapy. Response to anticancer treatment was assessed by Fluorescence Lifetime Imaging, FLIM method that exploits the intrinsic auto-fluorescence molecular properties of NAD(P)H. The first five recurrent GBM-EXP (rGBM-EXP) were treated with temozolomide (TMZ) and regorafenib; supplementary rGBM-EXP were treated with TMZ, regorafenib and lomustine. MGMT methylation status was assessed by pyrosequencing. Patients underwent second line chemotherapy regimens after surgery. Survival analysis took into account progression free survival (PFS) and overall survival (OS). RESULTS GBM-exp from three patients, out of five tested for regorafenib and TMZ, resulted sensitive to regorafenib ex vivo. All the three patients were treated with regorafenib at second line. In all the three patients progression occurred after 3 months from the start of regorafenib [median PFS 180 days]. GBM-exp from two patients, out of five tested for TMZ and regorafenib, resulted resistant to regorafenib ex vivo: both patients were treated with regorafenib and experienced progression earlier [median PFS 70.5 months]. Kaplan Meier analysis showed a significant difference in PFS between patients defined as "sensitive" in the rGBM-EXP assay and the "resistant" (p=0.04). Four supplementary patients-derived rGBM-EXP were tested for temozolomide (TMZ), regorafenib, and lomustine. For two patients, the tumor was still sensitive to TMZ and patients was rechallenged with TMZ treatment for the second line (patient 6 recurred one month after the end of RT; patient 7 recurred 3 years after first-line TMZ discontinuation). Patient 9 received regorafenib as second-line treatment since the tumor resulted sensitive to regorafenib in the r-GBM-EXP assay. Analysis of correlation between ex vivo results and the outcome will be performed in the next months. Interestingly, patients recurring during first-line chemotherapy with TMZ showed a higher rate of r-GBM-EXPs resistant to TMZ (71%) than patients recurring several months after TMZ discontinuation (25%). CONCLUSION Preliminary results showed a promising correlation between sensitivity observed ex vivo and in vivo. Supplementary patients and conventional or targeted options have to be analysed in order to assess whether r-GBM-EXP assay may drive second line options in the clinical setting.