P11.25.B Adjuvant high precision hypofractionated radiotherapy for resected brain metastases: single-institutional experience
Authors: Villalobos Monardes M , Comas Anton S , Álvarez Gracia A , Rosales Gonzalez H , Mañes Garcia A , Molero Savall J , Jové Teixido J , Moreno Lopéz S , Meca Santamaria G , Rodríguez Troyano A , Quintana Déniz M , Villà Freixa S 
Published: September 2022

Abstract

Background
The proportion of patients with solid tumor who develop brain metastases may be as high as 35%. Whenever possible, resection should be the first treatment option. Unfortunately, resection alone has recurrence rates up to 50-60%. In order to improve local control, adjuvant radiation to the surgical cavity is highly recommended. Single dose stereotactic radiosurgery (SRS) as well as hypofractionated stereotactic radiotherapy (HFSRT) have shown one-year local control rates from 70 to 90% with low incidence of radiation-induced toxicity. High precision hypofractionated radiotherapy (HFRT) using Volumetric Modulated Arc Therapy (VMAT) combines sharp dose gradients of SRS with a fractionated scheme, allowing high radiation doses per fraction while minimizing adverse events. Therefore, it could be used as an alternative to SRS for target volumes larger than 3 cm or close to sensitive brain areas. This study aims to analyze control parameters and toxicity of High precision HFRT after brain metastasis resection.

Material and Methods
We retrospectively analyzed 38 patients diagnosed with brain metastases underwent complete or subtotal surgical resection followed by adjuvant High precision HFRT between January and December 2019 at Catalan Institute of Oncology, Badalona. Radiation was delivered using VMAT technique with 6 MV photon beams. Patient immobilization was achieved using commercial radiotherapy-thermoplastic-mask and daily image guide control with CBCT (cone beam computed tomography) was performed. Statistical analysis was performed with SPSS.PASW.Statistics.v18.

Results
We identified 38 patients (47.4% men, 52.6% women) with a median age at diagnosis of 61 years [37 - 83 years]. Most of the primary neoplasms were from lung (50%) and breast cancer (24%). The median size of cavities was 10,5cc [0.4 - 75.5cc]. Radiation scheme was selected depending on size and location of the surgical cavity, primary tumor histology and patient’s performance status. Forty-two percent of patients received 27 Gy/3 fractions, 39% received 24 Gy/3 fractions and 7% received 18Gy/3fractions. The remaining four patients received 35 Gy/5fr (3%), 15 Gy/3fr (3%), 16 Gy/2fr (3%) and 30Gy/10fr (3%) respectively. With a median follow-up of 9.9 months, brain recurrence was observed in 23 patients (60%), with only 7 patients (18.4%) showing local relapse at surgical cavity. One-year local control rate was 81% for all patients. Radiation necrosis was confirmed by Positron Emission Tomography in 3 patients (7.8%). Leptomeningeal disease was observed in 5 patients (13.2%). No significant differences were observed between radiation schemes nor primary tumor histology.

Conclusion
Surgery followed by High precision HFRT delivered with VMAT technique is an effective and safe treatment alternative to SRS for selected patients with brain metastases.