From July 2019 to July 2021, 30 poor prognosis patients affected by GBM were treated by SIB-hypo-RT; 25 were evaluated in the present analysis due to a minimum follow up of 6 months. The median age and KPS were 65 years and 60%, respectively. At 15 months median follow-up, 14 patients (56%) were alive: 3 (12%) showed partial treatment response, 3 (12%) with stable disease and 8 (32%) with progression disease. The median OS was 13 months (95%CI 9.8-na) and 1-year OS was 54% (95%CI 31-73%); the median PFS was 8.4 months (95%CI 5.8-11.9) and 1-year PFS was 23% (95%CI 7-44%). No acute or late neurological side effect grade ≥ 2 were reported. Grade 3-4 hematologic toxicity occurred in 3 cases.
Of the 17 cases of disease progression, 8 received re-irradiation followed by second line systemic therapy (regorafenib or fotemustine), 3 received regorafenib alone and 6 were evaluated for best supportive care
Seven significant variables in univariate analysis (age, RPA, multifocal tumor, resection, MGMT status, GTV and PTV) were entered into multivariable model. As a result, MGMT unmethylation (HR: 0.61, 95%CI: 0.02-13.66, p=0.05), GTV > 50cc (HR: 4.83, 95%CI0.83-27.88, p=0.01) and PTV >200cc (HR:2.14, 95%CI: 0.01-9.87, p=0.02) were significant negative prognostic factors for survival.
Six significant variables in univariate analysis (mass effect, multifocal tumor, surgery, resection, MGMT status and PTV) were entered into multivariable model. As a result, multifocal tumor (p=0.05), incomplete resection (p=0.01), MGMT unmethylation (p=0.03) and PTV >200cc (HR:1.99, 95%CI: 0.26-5.37, p = 0.05) were significant negative prognostic factors for disease progression.