Session Item

Whole brain radiation therapy (WBRT) still represents the standard treatment for multiple brain metastases (BM). The hippocampal sparing WBRT (HS-WBRT) technique using Tomotherapy has shown a significantly lower memory decline in 4-months assessment compared to standard WBRT. The aim of the present study is to retrospectively evaluate intra and extra-hippocampal recurrences of disease of our HS-WBRT cohort.

Data were retrospectively collected from a cohort of patients (pts) who underwent HS-WBRT at a single institution from 2016 to 2021. Inclusion criteria were: 1) diagnosis of BM; 2) Karnofsky Performance Status (KPS)>60; 3) life expectancy more than 6 months; 4) available brain magnetic resonance imaging (MRI) before RT. Treatment was performed using TomoHelical scheduled in 30 Gy in 10 or 12 fractions. An additional cohort of pts with Small Cell Lung Cancer Limited Disease primaries underwent Prophylactic Cranial Irradiation (PCI) using HS-WBRT TomoHelical scheduled in 25 Gy in 10 fractions was also analyzed. Both cohorts signed a written informed consent. Oncological outcomes were clinically and radiologically assessed every 3 to 6 months after the end of HS-WBRT.  Toxicity was graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events version 4.0.

One-hundred fifty pts matched inclusion criteria, 120 pts in cohort 1 and 30 pts in cohort 2. Most of pts (70/120, 58%) underwent concomitant systemic therapies. 62/120 (62%) had KPS 90, 41/120 (34%) KPS 100, 11/120 (9%) KPS 80 and 5 (4%) KPS 70-60. Median dose to hippocampus was 7.6 Gy (range 6.4-14.5), median volume was 2.2 cc (range 0.72-8.37) and maximum dose was 14.75 Gy (range 7.65-27.77). Thirty-two pts (27%) experienced a brain recurrence. Of them, 23 (23/32, 72%) were extra-hippocampal and 2 (6%) were exclusively intra-hippocampal. Median time to recurrence was 7 months (range 0-23). After a median follow up of 6.3 months (range 0-23), 68 pts (57%) were dead, 32 pts (27%) had a relapse. The most common toxicities were headache, fatigue, and nausea. Overall, 10/120 (8%) pts experienced a G1 toxicity and 2/120 (2%) a G2 toxicity. In cohort 2, median dose to hippocampus was 7.41 Gy (range 6.4-9.1), median volume was 2.26 cc (range 0.74-8.38) and maximum dose was 14.54 Gy (range 11.59-20.4). One pt (3%) experienced extra-hippocampal brain disease.

Given the growing potential for prolonged survival with metastatic disease, identifying strategies to reduce treatment-associated side effects is of increasing significance. In the present study, according with published literature, HS-WBRT shows a durable intracranial disease control with tolerable side effects. A small risk of additional intra-hippocampal recurrence seems to be justified by memory preservation reported in numerous studies on HS-WBRT.