Research Associate NYU Langone Medical Center, New York, United States
Introduction: Dose selection for brain metastases (BM) stereotactic radiosurgery (SRS) classically has been based on tumor diameter with reduction of dose in the settings of prior brain irradiation, larger tumor volumes, critical brain location, and larger number of metastases. However, retrospective series have shown local failure rates to be potentially as high as 50%. Using competing risk analysis, this study aims to report the local control (LC) and predictors when a low margin dose was administered.
Methods: From 2014 to 2020. We reviewed 111 patients with 704 tumors who had low-margin dose radiosurgery, defined as ≤ 14Gy. Patient, tumor, and treatment characteristics were collected, and local control was correlated with demographic, clinical, and dosimetric data.
Results: Mean patient age was 63 years (22-89); histology of the main primary cancer types was lung in 55 (49%), breast in 32 (28%), melanoma in 11 (9%), and others in 13 patients (11.7%). The median tumor volume was 0.04cc (0.002 to 26.31 cc), and the median margin dose was 14 Gy (range 10-14). The local control rates at 1 and 2 years were 93% and 74% respectively. On competing-risk regression analysis, a volume larger than 0.065cc (diameter >5 mm), melanoma histology, and a margin dose lower than 13 Gy were significant predictors of local failure (LF). Adverse radiation effects (AREs) were identified in 12 (1.8%) patients who had received prior WBRT.
Conclusion : It is feasible to achieve acceptable local control in BMs with low-dose SRS. Larger volumes, melanoma pathology, and margin dose, appear to be predictors for LF (local failure). The value of low-dose radiosurgery may be in the palliative management of patients with higher numbers of small tumors with the aim of brain tumor control and functional preservation.
