Outcomes of Hypofractionated Stereotactic Radiotherapy for Small and Moderate-Sized Brain Metastases: A Single-Institution Analysis

Abstract

BackgroundStereotactic radiosurgery (SRS) is the standard treatment for limited intracranial metastases. With the advent of frameless treatment delivery, fractionated stereotactic radiotherapy (FSRT) has become more commonly implemented given superior control and toxicity rates for larger lesions. We reviewed our institutional experience of FSRT to brain metastases without size restriction.MethodsWe performed a retrospective review of our institutional database of patients treated with FSRT for brain metastases. Clinical and dosimetric details were abstracted. All patients were treated in 3 or 5 fractions using LINAC-based FSRT, did not receive prior cranial radiotherapy, and had at least 6 months of MRI follow-up. Overall survival was estimated using the Kaplan–Meier method. Local failure and radionecrosis cumulative incidence rates were estimated using a competing risks model with death as the competing risk. Univariable and multivariable analyses using Fine and Gray’s proportional subdistribution hazards regression model were performed to determine covariates predictive of local failure and radionecrosis.ResultsWe identified 60 patients and 133 brain metastases treated at our institution from 2016 to 2020. The most common histologies were lung (53%) and melanoma (25%). Most lesions were >1 cm in diameter (84.2%) and did not have previous surgical resection (88%). The median duration of imaging follow-up was 9.8 months. The median survival for the whole cohort was 20.5 months. The local failure at 12 months was 17.8% for all lesions, 22.1% for lesions >1 cm, and 13.7% for lesions ≤1 cm (p = 0.36). The risk of radionecrosis at 12 months was 7.1% for all lesions, 13.2% for lesions >1 cm, and 3.2% for lesions ≤1 cm (p = 0.15).ConclusionsFSRT is safe and effective in the treatment of brain metastases of any size with excellent local control and toxicity outcomes. Prospective evaluation against single-fraction SRS is warranted for all lesion sizes.

Outcomes of 30 Gy/5 Fr Hypofractionated Stereotactic Radiation Therapy for Small Brain Metastases (≤2 cm)

“…The crude overall risk of permanent morbidity or necrosis necessitating craniotomy after SRS for BMs is reported to be 4.7% to 7% (11,33,34). In prior research containing small lesions treated with SRT, the risk of symptomatic RN was very small, with some reports demonstrating no evidence of symptomatic RN (6)(7)(8)19). This is in line with our findings, implying that a prescription of 30 Gy/5 Fr is associated with acceptable toxicity.…”

“…To the best of our knowledge, this is the first study to report results of HFSRT at doses similar to those used in traditional SRS and limited to small BMs. A few cases of relatively small-size metastases were reported in previous investigations of clinical outcomes of treatment of BMs in general (6)(7)(8)(9). Most of the cases in those studies included inconsistent prescriptions as well as postoperative and post-WBRT cases.…”

“…Yan M et al reported on HFSRT of 133 metastases (21 lesions ≤1 cm and 112 lesions >1 cm) and showed that at 12 months, local failure was 17.8% for all lesions, 22.1% for lesions >1 cm, and 13.7% for lesions <1 cm (7). The prescriptions were not standardized and the results were based on groups that included postoperative lesions.…”

“…HFSRT, currently used for relatively small lesions in addition to large tumor lesions, allows for great local control (LC) and minimizes the risk of symptomatic radiation brain necrosis. In this context, some results have been observed (6)(7)(8)(9). With high-dose RT, radiation necrosis (RN) is the most frequent long-term toxicity occurring between 6 months and several years after SRS/fSRS, with a median time to onset of approximately a year (2).…”