PREDICTORS OF TUMOR DYNAMICS DURING A COURSE OF 30-FRACTION RADIOTHERAPY FOR GLIOBLASTOMA

Abstract We aim to identify predictors of tumor dynamics during radiotherapy for glioblastoma. METHODS: This is a prospective serial MRI study in patients with MRIs were obtained at planning (F0), fraction-10 (F10), and fraction-20 (F20). The metrics (relative F0) assessed included: relative gross volume (GTV) changes (Vrel) migration distance (dM). RESULTS: 129 included this study. Median GTV was 20.9cc F0, 17.6cc F10 (Vrel 0.85), 16.1cc F20 0.78). Patients no corpus-callosum involvement (CCI) (vs CCI) had more marked reduction: Vrel 0.82 vs 1.02 (P=0.05), 0.77 0.88 (P=0.03). total resection (GTR) reduction subtotal (STR) biopsy (Bx)): 0.78, 0.85 1.07 (P=0.001), 0.69, 0.80, 1.04 (P=0.001). median dM 4.7mm both F20. CCI larger CCI): 41% 12% dM>10mm (P=0.01), 45% 9% (P<0.001). At F20, 0%, 25% 19% GTR, STR Bx (P=0.002). Age, sex, MGMT methylation IDH-mutation status not associated treatment. CONCLUSION: extent surgery predict dynamics, which may allow us better select who benefit the most from re-planning/ treatment adaptation radiotherapy.