# Conformal Partial Brain Irradiation Versus Stereotactic Radiation Therapy in the Management of Resected Brain Metastases: A Retrospective Study

## TL;DR

This study compares conformal partial brain irradiation and stereotactic radiation therapy for brain metastases after surgery, finding that conformal partial brain irradiation may reduce recurrence and radiation necrosis.

## Contribution

The study provides evidence that conformal partial brain irradiation may be more effective than stereotactic radiation therapy in reducing local recurrence and radiation necrosis after brain metastasis surgery.

## Key findings

- Conformal partial brain irradiation had a 0% local recurrence rate compared to 21.9% with stereotactic radiation therapy.
- Conformal partial brain irradiation had a 0% radiation necrosis rate compared to 21.9% with stereotactic radiation therapy.
- The mean cavity volume treated with conformal partial brain irradiation was significantly larger than with stereotactic radiation therapy.

## Abstract

Introduction: The standard of care after resection of a single brain metastasis is to treat the cavity with stereotactic radiation therapy (SRT) to minimize the risk of recurrence. However, a prospective randomized trial of SRT demonstrated higher than expected rates of local recurrence, possibly due to geographic miss. Conformal partial brain (CPB) irradiation using conventional fractionation is an alternate technique that allows a larger margin of healthy tissue to be safely irradiated, potentially decreasing the risk of tumor recurrence. We performed a retrospective chart review to compare the results between CPB and SRT treatments.

Methods and materials: Patients receiving postoperative cranial radiotherapy within two months of a brain metastasis resection from 2015 to 2022 were eligible for this retrospective single-institution analysis. Fifty-seven patients met the eligibility criteria (SRT: n=32; CPB: n=25). SRT patients were treated using a robotic linear accelerator with a median dose of 24 Gy in 3 fractions. The median prescribed dose for the CPB group was 33 Gy in 11 fractions.

Results: The mean follow-up was 19.9 months. The crude rate of local recurrence rate was 21.9% (SRT) versus 0% (CPB) (p<0.013). The crude rate of radiation necrosis (RN) was 21.9% (SRT) versus 0% (CPB) (p<0.013). The mean cavity volume was 13 cc (SRT) versus 73 cc (CPB) (p<0.001). Most cases of RN were asymptomatic, although one patient suffered grade 4 status epilepticus.

Conclusion: In this single-institution cohort, CPB radiation therapy was statistically associated with a lower risk of both local failure and radiation necrosis as compared to SRT. Despite the cavity being much larger, none of the CPB patients suffered either local failure or radiation necrosis. Postoperative CPB irradiation may be beneficial for large cavity sizes or when it is difficult to delineate the tumor bed.