ESTRO 2021 Abstract Book

S881

ESTRO 2021

1 Instituto Português de Oncologia do Porto, Radiotherapy Department, Porto, Portugal; 2 Instituto Português de Oncologia do Porto, Cancer Epidemiology Group, Porto, Portugal; 3 Instituto Português de Oncologia do Porto, Medical Physics Department, Porto, Portugal; 4 Clínica de Radioncologia Madalena Paiva, Radiotherapy Department, Ponta Delgada, Portugal Purpose or Objective Brain metastasis are the most common malignant brain tumor in adults. The use of radiosurgery for the treatment of brain metastasis has proved to be both effective and safe. This institution based study intends to characterize patterns of progression and its treatments as well as to identify positive and negative factors contributing to progression and survival. Materials and Methods Patients submitted to radiosurgery for brain metastasis treated at our institution between January 2013 and December 2019 were retrospectively reviewed. Dose and fractionation were selected according to lesion size and proximity to OAR’s. Survival analysis was carried using Kaplan-Meier method; univariate and multivariate analysis were performed. Results Ninety-seven patients with 159 lesions were included. Median age was 61 (36-86) years, with a PS ≤80% in 24% of patients. The most common primary tumors were lung (63%), breast (16%), melanoma (7%) and renal cell carcinoma (7%). Sixty (62%) patients were treated for a single brain metastasis, 30 (31%) for 2-3 lesions and 7 (7%) for >3 lesions. The majority of patients had a Graded Prognosis Score (GPA) between 1.5-3 (89%). Of the 159 lesions treated, 77% had a diameter ≤20mm. A single fraction SRS was performed in 132 lesions (83%), with a median dose of 21 (12-24) Gy and a median GTV volume of 0.6 (0.1-27.8) cm 3 ; 3 fractions was planned for 18 lesions (11%), with a median dose of 27 (24-27) Gy and a median GTV volume of 3.3 (0.4-11.6) cm 3 ; 9 lesions were treated with 5 fractions with a median dose of 30 (20-30) Gy and a median GTV volume of 5.6 (1.0-32.0) cm 3 . Eighty five patients were eligible to follow up. Median follow up was 21 months. OS, local PFS and cerebral PFS at 1y were 73, 67 and 41%, respectively. Local, regional and cerebral progression rates were 40, 54 and 78%, respectively. Local progression was treated with salvage radiosurgery (18%), WBRT (29%) or best supportive care. Of the patients who recur regionally, 51% were submitted to radiosurgery and 59% to WBRT. In a metastasis based analysis, 5% of lesions had progressed at 4 months and 15% at 12 months. Univariate analysis identified age (≥60) as a predictor of worst OS (HR 1.67, IC95% 1.03-2-71), although non significant in the multivariate analysis. GTV volume >2cm 3 was correlated with increased local progression (HR 2.07, IC95% 1.12-3.82) in both uni and multivariate analysis. Of note, neither GPA score, number of lesions nor total volume of cerebral disease were associated with survival or progression outcomes. Conclusion We report 1y LC of 67% for brain metastasis treated with radiosurgery. Of the 78% of patients who had a regional progression, more than half of the patients were still candidate for radiosurgery. PO-1060 Cranial radiotherapy as salvage treatment in relapsed primary CNS lymphomas M. Volpini 1 , J. Song 1 , R. Samant 1,2 , D. MacDonald 3 , V. Nair 1,2 1 University of Ottawa, Radiation Oncology, Ottawa, Canada; 2 Ottawa Hospital Research Institute, Radiation Oncology, Ottawa, Canada; 3 University of Ottawa, Hematology, Ottawa, Canada Purpose or Objective Primary CNS lymphoma (PCNSL) is a rare disease accounting for 3% of all CNS malignancies. Standard of care for PCNSL is upfront high-dose methotrexate (HD-MTX) chemotherapy for eligible patients, while cranial radiotherapy (RT) is reserved for salvage. In this retrospective study, we aimed to investigate the safety and efficacy of salvage cranial RT. Materials and Methods Patients diagnosed with PCNSL, who received upfront HD-MTX chemotherapy and salvage cranial RT after disease relapse between 1995 and 2017 were selected. Patient demographics and treatment data were collected and radiologic response to cranial RT was assessed. Results A total of 23 patients were selected (median age 59.9 years) and 21 patients received salvage cranial RT, among which 47.6% achieved complete response and 42.9% achieved partial response. Patients who had response to chemotherapy were more likely to achieve complete response (62.5%) than those who did not (30.7%). Higher dose to the whole brain (>30Gy) was associated with higher rate of complete response (53.3%) than lower dose (≤30Gy, 33.3%), while boost dose to the gross disease was associated with higher rate of complete response (57.1%) compared with no boost dose (28.6%). Four patients (19.0%) sustained at least grade 2 treatment-related neurotoxicity. Median overall survival, defined as time from start of salvage RT to death or last follow-up, was 20.7 months (range 1.9 to 147 months) among the entire cohort. Conclusion PCNSL patients who relapsed following upfront HD-MTX chemotherapy showed a high rate of response to salvage cranial RT, especially those receiving >30Gy to the whole brain. Further study is necessary to elucidate the role of salvage cranial RT in these patients. PO-1061 Acute relative lymphopenia is associated with poor survival in GBM following postoperative chemo-RT S. Arcangeli 1 , R. Mapelli 1 , C. Julita 1 , S.P. Bianchi 1 , R. Lucchini 1 , M. Midulla 1 , F. Puci 1 , J. Saddi 1 , S. Trivellato 2 , D. Panizza 2 , E. De Ponti 2 1 University of Milan Bicocca, Radiation Oncology, Milan, Italy; 2 S. Gerardo Hospital, Medical Physics, Monza, Italy