Stereotactic Radiation Therapy for Brain Metastases: Factors Affecting Outcomes and Radiation Necrosis

SIMPLE SUMMARY: Brain metastases constitute a severe event in many patients affected by solid tumors. Indeed, even in those cases in which the original disease is sensitive to a systemic treatment, the particular vascularization of the brain may limit its efficacy in the site. Stereotactic radiation therapy (SRT) plays a major role in the multidisciplinary management of oncological patients with brain metastases (BMs). SRT is generally delivered in single or multiple (3–5) fractions. Data from 87 analyzed patients treated at our institution suggest that this technique is characterized by a good effectiveness in local control and patients with stable extracranial disease benefit most from SRT. Tumor histology does not affect local control. Radiation necrosis (RN) occurrence was registered in 16% of treated sites, and it appeared to be related to left location and adenocarcinoma histology, while chemotherapy reduced the risk. When RN occurs, prompt recognition is needed to establish a treatment. ABSTRACT: Stereotactic radiation therapy (SRT) is a proven effective treatment for brain metastases (BM); however, symptomatic radiation necrosis (RN) is a late effect that may impact on patient’s quality of life. The aim of our study was to retrospectively evaluate survival outcomes and characterize the occurrence of RN in a cohort of BM patients treated with ablative SRT at Federico II University Hospital. Clinical and dosimetric factors of 87 patients bearing a total of 220 BMs treated with SRT from 2016 to 2022 were analyzed. Among them, 46 patients with 127 BMs having clinical and MRI follow-up (FUP) ≥ 6 months were selected for RN evaluation. Dosimetric parameters of the uninvolved brain (brain without GTV) were extracted. The crude local control was 91% with neither clinical factors nor prescription dose correlating with local failure (LF). At a median FUP of 9 (1–68) months, the estimated median overall survival (OS), progression-free survival (PFS), and brain progression-free survival (bPFS) were 16, 6, and 9 months, respectively. The estimated OS rates at 1 and 3 years were 59.8% and 18.3%, respectively; bPFS at 1 and 3 years was 29.9% and 13.5%, respectively; PFS at 1 and 3 years was 15.7% and 0%, respectively; and local failure-free survival (LFFS) at 1 and 3 years was 87.2% and 83.8%, respectively. Extracranial disease status was an independent factor related to OS. Fourteen (30%) patients manifested RN. At multivariate analysis, adenocarcinoma histology, left location, and absence of chemotherapy were confirmed as independent risk factors for any-grade RN. Nine (20%) patients developed symptomatic (G2) RN, which improved or stabilized after 1–16 months of steroid therapy. With prompt recognition and, when necessary, medical therapy, RN radiological and clinical amelioration can be obtained.