ESTRO 2022 - Abstract Book

S635

Abstract book

ESTRO 2022

Purpose or Objective BACKGROUND: Neural stem cells (NSCs) are involved in the brain's ability to regenerate and are located in the subventricular zone (SVZ) and subgranular zone (SGZ) of the hippocampus (HPC), known as the primary neurogenic niches of the brain. It is believed that irradiating these areas inhibits the repair capacity of the brain. Indeed, it has recently been shown in glioma patients that increased radiation dose on the neurogenic niches decreases OS. In this study, we investigate the effects of radiation dose in neurogenic niches on OS in a cohort of patients with brain metastases. Materials and Methods We included 262 patients with brain metastases from various primary tumors, who underwent radiotherapy at UMC Utrecht between November 2014 and July 2020. NSC-regions were automatically delineated on T1 MR images using CAT12. OS was analyzed using univariable and multivariable Cox regression, corrected for covariates: age, Karnofsky Performance Status (KPS), number of metastases and the use of chemotherapy or immunotherapy (see table 1). Results All patients received any radiotherapy in neurogenic niches (SVZ: 0.02Gy-46.75Gy EQD2, HPC: 0.02Gy-42,04Gy EQD2). In univariable analyses, the hazard ratio (HR) was 1.035 per Gy (P = 0.025 [95% confidence interval (CI), 1.008 – 1.062]) for the mean dose in the SVZ, and 1.014 per Gy (P = 0.258 [95% CI, 0.990 – 1.038 ]) for the mean HPC dose. Multivariable analyses showed only statistically significant HRs for KPS and administration of immunotherapy.

Variable

Hazard ratio (HR) 95%-Confidence interval (CI) P-value

Age

1.015 0.975 0..941

0.999 – 1.031 0.965 – 0.984 0.602 – 1.470 0.851 – 1.600 0.409 – 0.753 0.989 – 1.052 0.988 – 1.053

0.063

Karnofsky Performance Status (KPS)

<0.001

Number of mets >4 vs. 1- 3

0.788 0.338

Administration of chemotherapy Yes vs. No 1.167 Administration of immunotherapy Yes vs. No 0.555

<0.001

RT dose on hippocampus in Gy

1.020 1.020

0.220 0.220

RT dose on SVZ in Gy

Conclusion In this study, we showed that irradiation of the SVZ or HPC is not correlated with OS in patients with brain metastases after correcting for covariates. We confirmed the prognostic value of KPS and immunotherapy in OS in patients with brain metastases. In contrast to glioma, this suggest that there is no role for neurogenic niches avoidance in stereotactic irradiation of brain metastases regarding OS

MO-0725 Hippocampal Sparing Wbrt: Trade-Off Between Tumor Control And Quality Of Life?

G. Corrao 1 , L. Bergamaschi 1 , V.E. Pierini 1 , A. Ferrari 2 , G. Piperno 2 , G. Marvaso 1 , F. Emiro 3 , M. Pepa 4 , S. Gandini 5 , F. Cattani 3 , R. Orecchia 6 , B.A. Jereczek-Fossa 2 1 IEO, European Institute of Oncology IRCCS; University of Milan, Division of Radiation Oncology; Department of Oncology and Hematoncology, Milan, Italy; 2 IEO, European Institute of Oncology IRCCS, Division of Radiation Oncology, Milan, Italy; 3 IEO, European Institute of Oncology IRCCS, Unit of Medical Physics, Milan, Italy; 4 IEO, European Institute of Oncology IRCCS, Division of Radiation Oncology; Department of Oncology and Hematoncology, Milan, Italy; 5 IEO, European Institute of Oncology IRCCS, Department of Experimental Oncology, Milan, Italy; 6 IEO, European Institute of Oncology, IRCCS, Scientific Directorate, Milan, Italy Purpose or Objective Hippocampal sparing whole-brain radiotherapy (HS-WBRT) technique has shown a significantly lower memory decline in 4- months assessment compared to standard WBRT with comparable local control of disease. The aim of the present study is to retrospectively evaluate intra and extra-hippocampal recurrences of disease in our HS-WBRT cohort, evaluating the association with clinical, pathological and radiological variables.