Main Session
Sep 27
PQA 01 - Gastrointestinal Cancer and Central Nervous System

2204 - 27 Gy in 3 Fractions Stereotactic Radiotherapy to Metastatic Brain Lesions Less Than 2 Cm: A Single Institution Experience

03:00pm - 04:00pm ET
Poster Hall - Exhibit Hall A
Screen: 5
POSTER

Presenter(s)

Jimmy Sebaaly, MD Headshot
Jimmy Sebaaly, MD - American University of Beirut, Beirut, Beyrouth

J. Sebaaly V1, R. Khodor2, A. H. Shmoury3, L. Bodgi2, M. Charafeddine2, T. Mobayed4, T. Al Bitar3, Z. Dandash2, L. Hilal4, Z. Ayoub4, T. A. Eid2, O. Mohamad4, W. Jalbout2, M. Al beainy2, Z. Reda3, and B. Y. Youssef2; 1American University of Beirut, Beirut, Beyrouth, Lebanon, 2American University of Beirut Medical Center, Beirut, Lebanon, 3American University of Beirut Medical center, Beirut, Lebanon, 4American University of Beirut, Beyrouth, Lebanon

Purpose/Objective(s): Stereotactic radiation therapy (SRT) is a well-established treatment for patients with limited brain metastases. Fractionation is typically selected based on lesion size and location, with a single 20-Gy fraction being widely used for lesions =2 cm. At our institution, patients with multiple brain metastases of varying sizes, all <3 cm, are treated using a single-isocenter SRT plan prescribing 27 Gy in three fractions, with the aim of streamlining treatment planning and delivery. This study aims to evaluate local control and the incidence of radionecrosis in small brain metastases (maximum dimension =2 cm) treated with 27 Gy in 3 fractions.

Materials/Methods: From January 2020 to September 2025, 65 patients received SRT 27 Gy in 3 fractions for 210 small brain lesions (=2cm). 4 patients have also had prior whole brain radiation treatment (WBRT). Local progression was defined as an increase in size of the lesion on follow up brain MRI, and radionecrosis was evaluated using follow-up contrast-enhanced brain MRI and multiparametric MRI techniques, including spectroscopy, diffusion, and perfusion. Local control was estimated using the Kaplan–Meier method. Radionecrosis was analyzed descriptively and reported as proportions.

Results:

A total of 210 small lesions were analysed. The mean size of the lesions was 0.95cm (range 0.1 – 2cm). Over a median follow up of 16.6 months, one local progression was observed after 36.3 months. The 1- and 2-year actuarial local control rates were 100%.

9/210 lesions developed radionecrosis (4.3%), of which two have received WBRT prior to SRT and one has received SRT twice due to local progression before developing radionecrosis. Five lesions were treated with steroids, three required the use of bevacizumab, and one was refractory to medical treatment and was eventually resected.

Conclusion: In this single-institution series, SRT delivered as 27 Gy in three fractions for brain metastases =2 cm demonstrated local control and safety outcomes at least as good as single-fraction 20-Gy SRS. This regimen represents a practical and effective option for single-isocenter treatment of multiple brain metastases smaller than 3 cm.