ESTRO 2023 - Abstract Book

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ESTRO 2023

months after irradiation and died 4 months after irradiation. One patient who underwent WBI and did not receive intrathecal injection died of myocarditis triggered by infection two months after brain irradiation. Conclusion CSI was selected as basic planned salvage radiotherapy for CNS recurrent hematopoietic tumors in the institute. Specific indicators for choosing between CSI and WBI for radiotherapy of CNS recurrent hematopoietic tumors were not found in this review. Although WBI was performed in only 5 cases, only 1 case of CNS recurrence occurred, suggesting that WBI may be effective enough to prevent CNS recurrence when intrathecal injection is performed. Although both a small number, there were a few patients of presumed excessive irradiation field among the CSI cases, and a few patients of suspected insufficient irradiation field among the WBI cases. C. satragno 1 , A. Gonnelli 2 , D. Esposito 3 , A. Ginulla 4 , C. Scaffidi 4 , E. Cella 5 , M. Tagliamento 6 , N. Giannini 7 , G. Gadducci 7 , S. Valenti 8 , F. Giannelli 9 , A. Fozza 10 , E. Bennicelli 11 , P. Fiaschi 12 , S. Morbelli 13 , L. Roccatagliata 14 , F. Paiar 8 , S. Barra 10 , L. Belgioia 15 1 University of Genoa, Department of experimental medicine (DIMES), , Genoa, Italy; 2 Hospital of Pisa, University of Pisa, Department of Radiotherapy Oncology , Pisa, Italy; 3 IRCCS Policlinico San Martino, University of Genoa, Radiation Oncology Unit, Department of Health Sciences (DISSAL) , Genoa, Italy; 4 IRCCS Policlinico San Martino, University of Genoa, Radiation Oncology Unit, Department of Health Sciences (DISSAL), Genoa, Italy; 5 IRCCS Policlinico San Martino, Medical Oncology 2, Genoa, Italy; 6 University of Genoa, Department of Internal Medicine and Medical Specialties (DIMI), Genoa, Italy; 7 Hospital of Pisa, University of Pisa, Department of Radiotherapy Oncology, Pisa, Italy; 8 Hospital of Pisa, University of Pisa, Department of Radiotherapy Oncology , Pisa, Italy; 9 IRCCS Policlinico San Martino, Radiation Oncology Unit,, Genoa, Italy; 10 IRCCS Policlinico San Martino, Radiation Oncology Unit, Genoa, Italy; 11 IRCCS Policlinico San Martino, Medical Oncology 2 Genoa, Genoa, Italy; 12 IRCCS Policlinico San Martino Hospital, University of Genoa, Department of Neurosurgery, Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DINOGMI), Genoa, Italy; 13 IRCCS Policlinico San Martino, University of Genoa, Nuclear Medicine Unit, Department of Health Sciences (DISSAL) Genoa, Genoa, Italy; 14 IRCCS Policlinico San Martino Hospital, University of Genoa, Department of Neuroradiology, Department of Health Sciences (DISSAL), Genoa, Italy; 15 IRCCS Policlinico San Martino, University of Genoa, Radiation Oncology Unit, Department of Health Sciences (DISSAL) , Genoa, Italy Purpose or Objective The aim of the study was to retrospectively confirm that RT planned on pre-RT MRI might allow to spare more normal tissue without decreasing local tumor control, in order to prospectively evaluate the best standard and advanced MRI and metabolic imaging sequences for clinical tumor volume (CTV) adaptation. Materials and Methods We analyzed a retrospective cohort of patients with HGG treated from 2017 to 2020 to the two Institutes. All patients had a diagnostic MRI and an immediately post—surgery or pre-RT MRI. Patients were divided into two groups: in group A target volumes were contoured on diagnostic and post-surgery T2/FLAIR MRI, while in group B on pre-RT MRI. We analyzed gross tumor volume (GTV) and CTV volume, and the percentage increase between them. Moreover, we compared the two groups in terms of clinical-pathological characteristics and progression-free survival (PFS) and overall survival (OS). Results We analyzed 54 patients (25 group A, 29 group B). The median age of patients was 61 years (IQR 17,75), 93% had an ECOG PS of 0 or 1, 51 were symptomatic at diagnosis. Patients in group B had more frequently MGMT methylation (59 % vs. 28%, p=0.01) while less frequently frontal lobe involvement (60% vs. 24%, p=0.01). The median percentage increase between GTV and CTV was higher in group A than B: 431% (range 62%-7335%) vs 385% (range 53%-3174%), respectively. No significant difference in the pattern of relapse was observed, since >90% of disease recurrences were in-field in both groups. Median PFS and OS of the overall population were 9.5 months (95% CI 7 - 12) and 18.5 months (95% CI 16 - 24), respectively. Patients in group B had a significant better PFS as compared to those in group A (p=0.03), but similar OS. Nevertheless, imbalance in MGMT methylation status between the two groups was a major driver for PFS. Overall, 37 out of 51 patients had improvement in neurological symptoms (p<0.001), with no difference between the two groups (p=0.54). Conclusion Our data suggest that CTV adaptation to pre-RT MRI T2/FLAIR may allow to reduce RT volume, without affect symptoms relieving and disease control. Results from the prospective study will help identifying the best adaptation of CTV guided by T2/FLAIR, advanced MRI sequences, in order to optimize efficacy and safety of treatment planning. PO-1133 Potential role of pre-radiotherapy MRI for target delineation in high-grade gliomas

PO-1134 Repeated SRS with linac-based monoisocentric technique in recurrent intracranial metastases

L. Nicosia 1 , N. Giaj-Levra 1 , R. Mazzola 1 , F. Ricchetti 1 , E. Pastorello 1 , M. Rigo 1 , V. Figlia 1 , R. Ruggieri 1 , F. Alongi 1

1 IRCCS Sacro Cuore Don Calabria Hospital, Cancer Care Center, Advanced Radiation Oncology Department, Negrar, Italy

Purpose or Objective Stereotactic radiosurgery (SRS) or stereotactic fractionated radiotherapy (SFRT) are effective treatment options in the management of multiple brain metastases (BMs). Furthermore, modern mono-isocentric techniques allow the delivery of multiple stereotactic courses, in the event of intracranial failure. Nevertheless, limited data on the effectiveness and