ESTRO 38 Abstract book

S81 ESTRO 38

D. Yeboa 1 , J. Yu 2 , K.E. Liao 3 , J. Huse 4 , M. Penas-Prado 5 , B. Kann 2 , E. Sulman 6 , D. Grosshans 1 , J. Contessa 2 1 MD Anderson Cancer Center, Radiation Oncology, Houston, USA; 2 Yale University School of Medicine, Department of Therapeutic Radiology, New Haven, USA ; 3 MD Anderson Cancer Center, Health Services Department, Houston, USA ; 4 MD Anderson Cancer Center, Department of Pathology, Houston, USA; 5 National Institute of Health, Neuro-Oncology Branch, Bethesda, USA; 6 New York University, Radiation Oncology Department, New York, USA Purpose or Objective Molecular markers are redefining classification of lower grade gliomas and ushering in a paradigm shift in their management. Our objective was to evaluate the impact of histologic grade on patterns of care and treatment outcomes for 1p19q co-deleted gliomas. Material and Methods We evaluated 1,618 patients in the National Cancer Database diagnosed with 1p19q co-deleted gliomas from 2010 through 2014 and treated with surgery followed by radiation therapy (RT), chemotherapy (CT), or combined- modality therapy. Kaplan-Meier analysis and log-rank tests were used to assess OS over time. Cox proportional hazards regression modeling was used to assess associations between the World Health Organization (WHO) glioma grade and the outcome of death when adjusting for significant clinical covariates, with a p value <0.05 defining significance. Additionally, propensity score matching was done in an attempt to further balance patients by known covariates. Results Most patients with grade II tumors received surgery alone (51.0%), whereas most patients with grade III tumors (86%) received surgery or biopsy followed by a form of post- operative therapy ( p <0.001). In a propensity score matched cohort, the Cox multivariable proportional hazards model with frailty testing identified significant covariates were age, comorbidity, histology and grade. Patients ≥60 years had a higher likelihood of death as did those with at least one comorbidity. The hazard for death for grade III 1p19q co-deleted gliomas was about 3.6 times higher ([HR] 3.69, 95% confidence interval [CI] 2.03–6.68, p <0.001) than grade II 1p19q gliomas. Oligodendroglioma histology was associated with a lower likelihood of death (HR 0.40, 95% CI 0.23-0.70, p <0.001). Conclusion In conclusion, our study with one of the largest cohorts of specifically grade II versus grade III 1p19q co-deleted gliomas, provides relevant information on real-world outcomes in a national cohort. While we await the results of clinical trials such as CODEL and BN005, our study offers context regarding historical treatment patterns and outcomes in the community for 1p19q co-deleted gliomas. OC-0166 Cumulative metastases volume, not number of brain metastases predicts survival in melanoma patients J. Heitmann 1 , S.G.C. Kroeze 1 , O. Blanck 2 , S. Stera 3 , K.H. Kahl 4 , S. Gerum 5 , S.E. Combs 6 , A. Haap 7 , A. Claes 8 , M. Schymalla 9 , A. Grosu 10 , F. Eckert 11 , F. Lohaus 12 , N. Abbasi-Senger 13 , G. Henke 14 , M. Szuecs 15 , M. Geier 16 , N. Sundahl 17 , D. Buergy 18 , M. Guckenberger 1 1 University Hospital Zürich, Radiation Oncology, Zurich, Switzerland ; 2 Saphir, Radiosurgery Center, Gustow, Germany ; 3 University Hospital Frankfurt, Radiation Oncology, Frankfurt, Germany ; 4 Klinikum Augsburg, Radiation Oncology, Augsburg, Germany ; 5 University Hospital Munich, Radiation Oncology, Munich, Germany ; 6 Technical University Munich, Radiation Oncology, Munich, Germany ; 7 Charité University Hospital, Radiation Oncology, Berlin, Germany ; 8 University Medical Center Utrecht, Radiation Oncology, Utrecht, The Netherlands ; 9 Philipps University Marburg,

Radiation Oncology, Marburg, Germany ; 10 University Medical Center Freiburg, Radiation Oncology, Freiburg, Germany; 11 University Hospital Tübingen, Radiation Oncology, Tübingen, Germany; 12 University Hospital Dresden, Radiation Oncology, Dresden, Germany ; 13 University Hospital Jena, Radiation Oncology, Jena, Germany ; 14 Kantonsspital St. Gallen, Radiation Oncology, St. Gallen, Switzerland; 15 University Hospital Rostock, Radiation Oncology, Rostock, Germany; 16 Ordensklinikum Linz, Radiation Oncology, Linz, Austria; 17 Ghent University Hospital, Radiation Oncology, Ghent, Belgium; 18 University Hospital Mannheim, Radiation Oncology, Mannheim, Germany Purpose or Objective In 2017, Sperduto et al. proposed an updated Graded Prognostic Assessment for melanoma patients with brain metastases (molGPA score), which was validated by Nieder et al. in a cohort of 69 patients. However, both studies included many patients that received whole brain radiation therapy (WBRT). As melanoma patients are increasingly treated with stereotactic radiotherapy or radiosurgery (SRT) alone, we aimed to validate the score in a large cohort of 140 melanoma patients treated exclusively with SRT without WBRT, and concurrent targeted- or immunotherapy. Material and Methods We retrospectively analyzed data from the international database of efficacy and toxicity of combined SRT and immuno- or targeted therapy (TOaSTT). Patients that received a concurrent WBRT (n=5) with the SRT were excluded, as well as re-irradiations. The updated molGPA score was applied to our cohort to predict survival. The molGPA score included age (≥70 years or < 70 years), performance status, presence of extracranial metastases, BRAF mutational status and number of brain metastases. We used Kaplan-Meier curves to compare overall survival (OS) of groups defined by the score and compared by log rank test. Results 18 centers treated 140 melanoma patients between 05/2011 and 02/2018 with concurrent targeted- or immunotherapy and SRT for 327 brain metastases with a median of 1 (1-6) fractions and a median of 20 Gy (12- 30Gy). A median of 2 (1-30) metastases were treated per session with a median cumulative volume of 1.47cc (0.05- 24.54cc). The molGPA score could not be validated in our patient cohort (p = 0.199). The four groups defined by the score did not show a significant difference in OS, as the number of metastases did not influence survival. However, in univariate analysis, the cumulative volume of irradiated metastases was significantly associated with OS: the group with an irradiated cumulative brain metastases volume smaller than the median volume (1.5cc) survived significantly longer than the group with a larger than or equal to 1.5cc cumulative brain metastases volume (p = 0.02). Therefore, the number of brain metastases in the molGPA score was substituted with cumulative brain metastases volume. Using this combination of factors, the four modified molGPA score prognostic groups showed significantly different OS (logrank p = 0.02).