Clinical results and hematological predictors of linac-based stereotactic radiosurgery or fractionated stereotactic radiotherapy for brain metastasis in patients aged 75 years or higher: a retrospective study

This study aimed to evaluate prognostic factors including pre-radiosurgical blood count in elderly patients (EPs) with brain metastasis (BM) who were treated using linear accelerator (linac)-based, stereotactic radiosurgery (SRS) and fractionated stereotactic radiotherapy (fSRT) with a micro-multileaf collimator. Between January 2011 and November 2021, 101 consecutive elderly patients with BM were treated by linac-based SRS or fSRT using linac with a micro-multileaf collimator. EPs were defined as patients aged ≥75 years. The tumors originated from the lungs (n = 90, 89.1%), colon (n = 2, 2.0%), and others (n = 9, 8.8%) in these EPs. The median pretreatment Karnofsky Performance Scale (KPS) score was 80 (range: 40-100). The median follow-up time was 10 (range: 0-76) months, as was the median survival time. The 6-month and 1 and 2-year survival rates in the EP group were 58.3%, 43.2%, 28.5%, respectively. Freedom from local failure at 6 months and 1 and 2 years were 97%, 95%, and 91.5%, respectively. Freedom from distant failure at 6 months and 1 and 2 years in EPs were 70.6%, 59.4%, and 54.2%, respectively. A high neutrophil/lymphocyte ratio (NLR) >5.33 was an unfavorable predictor of prognosis for EPs with BMs treated with SRS and fSRT (p<0.001). In the EPs, the prognostic factors associated with prolonged survival time in the Cox proportional hazards model were being female and a good pretreatment KPS score. The findings of our study highlight the efficacy of linac-based SRS and fSRT with a micro-multileaf collimator in the treatment of EPs with BMs. NLR can be an important factor in treatment decisions for EPs with BMs.