ESTRO 2020 Abstract Book

S83 ESTRO 2020

A systematic literature search was performed, to identify studies with at least one ICI-RT arm and reporting information for the aforementioned outcomes. Whenever data on mono-RT arms were available, corresponding risk ratios were also calculated. A mixed-effects meta-analysis was then performed, to evaluate the importance of ICI and RT therapy administration sequencing, and of ICI agent class (PD-(L)1 vs. CTLA-4 Ab) and RT type on treatment outcomes. Results 37 studies with 3786 enrolled patients were identified. ICI- RT was associated with higher 1-year OS vs . mono-RT (Table 1). The only factor affecting treatment outcomes was the administration sequencing of ICI and RT combinations; the highest 1-year OS was observed for a concurrent regimen of the combination, followed by sequential regimens and mono-RT (67%, 51% and 30%, respectively). No differences in 1-year LC and RNR were found (Table 1). Table 1. Comparison of treatment outcomes for ICI-RT and mono-ICI

Incidence rate, % (95% CI): m ono-RT

Incidence rate, % (95% CI): ICI-RT Concurrent: 69 (60-78) (45-58) Unknown: 59 (52-66) Sequential: 52

Risk ratio (95% CI)

p- value

p- value

1- year OS

1.67 (1.40- 1.98)

32 (25-40)

<.0001

<.0001

> Conclusion Stereotactic radiotherapy leads to complete resolution of brain metastases during long-term follow-up, radioresistant histology was associated with slower regression. Volumetric analysis may have a role in identifying metastases at risk for subsequent progression. Volumetric regression ≥20% at 3 months post-SRT was predictive for subsequent local control and could therefore be suitable for the standardized assessment of volumetric response following SRT in clinical trials. PD-0171 Reduced-Dose Whole Brain Radiotherapy for the Primary Central Nervous System Lymphoma PD-0172 Radio/immuno-therapies of brain metastasis disease: A meta-analysis of efficacy and safety outcomes V. Voronova 1 , S. Lebedeva 2 , M. Sekacheva 3 , G. Helmlinger 4 , K. Peskov 1 1 M&S Decisions LLC, department of mathematical modeling, Moscow, Russian Federation ; 2 I.M. Sechenov First Moscow State Medical University, Institute of Pharmacy, Moscow, Russian Federation ; 3 I.M. Sechenov First Moscow State Medical University, Computational oncology group, Moscow, Russian Federation ; 4 AstraZeneca, Clinical Pharmacology & Safety Sciences- BioPharmaceuticals R&D, Boston, USA Purpose or Objective In the treatment of brain metastases, multiple clinical studies have demonstrated the advantages of combining immune checkpoint inhibitors with radiation therapy (ICI- RT) over radiotherapy alone (mono-RT). In the present research, we sought to: (i) compare efficacy (1-year overall survival (OS) and 1-year local control (LC)) and safety (radionecrosis rate (RNR)) outcomes for ICI-RT and mono-RT, across all relevant published clinical studies; and (ii) identify factors affecting these outcomes, using a quantitative meta-analysis approach. Material and Methods Abstract withdrawn

1- year LC

1.04 (0.88- 1.22) 1.60 (1.00- 2.56)

68 (46-86) 80 (73-87)

0.73

0.67

RNR 6 (2-13)

9.0 (5.0-14) 0.37

0.05

Conclusion ICI-RT combinations demonstrated higher efficacy and a comparable safety profile vs . mono-RT; superiority of concurrent combination regimens was shown. PD-0173 Ventricular – Subventricular zone involvement – A Predictive factor for survival in Glioblastoma V. Pareek 1 , R. Bhalavat 2 , M. Chandra 2 , N. Reddy 2 , Z. Moosa 2 , A. Rungta 2 , D. Kawale 2 , S. Patel 2 , L. Nellore 2 , K. George 2 , D. Borade 2 , K. Kalariya 2 , P. Bauskar 2 , N. Kumar 2 1 National Cancer Institute- AIIMS, Radiation Oncology, New Delhi, India ; 2 Jupiter Lifelines Hospital, Radiation Oncology, Thane, India Purpose or Objective MRI imaging is an essential tool in diagnosing glioblastoma and it can give various anatomical details related to disease. It gives an assessment of involvement of disease with ventricular – subventricular zone (VSVZ), subgranular (SGZ) and corpus callosum (CC). This study aims at assessment of survival outcomes in diseases involving neurogenic zones and corpus callosum and the associated prognostic factors. Material and Methods We retrospectively analyzed 376 adult patients treated for histologically proven Glioblastoma. MRI studies were assessed for the tumor volume and its association with the neurogenic zones and corpus callosum. Age of patient, comorbidities associated, performance status, extent of resection and radiation doses received by these structures were evaluated. Overall (OS) and progression free (PFS) survivals were calculated and analyzed with multivariate Cox analyses. Results