Image-Guided, Linac-Based, Surgical Cavity-Hypofractionated Stereotactic Radiotherapy in 5 Daily Fractions for Brain Metastases

BACKGROUND: Cavity stereotactic radiotherapy has emerged as a standard option following resection of brain metastases. However, the optimal approach with either single-fraction or hypofractionated stereotactic radiotherapy (HSRT) remains a significant question. OBJECTIVE: To report outcomes for 5-fraction HSRT to the surgical cavity, based on contouring according to a recently reported international consensus guideline. METHODS: Patients treated with cavity HSRT were identified from a prospective institutional database. Local brain control (LC), distant brain failure (DBF), leptomeningeal disease (LMD), and overall survival rates were determined. Univariate and multivariable analyses were performed on potential predictive factors. RESULTS: One hundred thirty-seven cavities in 122 patients were treated at amedian total dose of 30 Gy (range, 25-35 Gy). The median follow-up was 16mo(range, 1-60 mo). Nonsmall cell lung cancer was the most common histology (44%), followed by breast cancer (21%). In 57% of surgical cavities, the preoperative tumor diameter was >3 cm. One-year LC, DBF, LMD, and overall survival rates were 84%, 45%, 22%, and 62%, respectively. Multivariable analyses identified colorectal (hazard ratio [HR] 4.1, P = .0066) and melanoma (HR 2.4, P = .012) metastases as predictors of local recurrence; preoperative tumor diameter >2 cm (HR 8.9, P = .012) and absence of targeted therapy (HR 4.4, P = .03) as predictors of DBF; and breast cancer histology (HR 2.1, P = .05) and subtotal resection (HR 2.6, P = .009) as predictors of LMD. Symptomatic radiation necrosis was observed in 7 patients (6%). CONCLUSION: High rates of LC were observed following this 5-fraction HSRT regimen. Superiority as compared to single-fraction SRS requires a randomized trial.