Radiation Therapy Practice Patterns for Brain Metastases in the United States in the Stereotactic Radiosurgery Era

Abstract

Purpose: Utilization of stereotactic radiosurgery (SRS) for brain metastases (BM) has increased, prompting reassessment of whole brain radiation therapy (WBRT). A pattern of care analysis of SRS and WBRT dose-fractionations was performed in patients presenting with BM at the time of cancer diagnosis.

Methods and materials: Adults with BM at cancer diagnosis between 2010 to 2015 and no prior malignancy were identified in the National Cancer Database. SRS was defined using published thresholds. Short (ShWBRT), standard (StWBRT), and extended (ExWBRT) dose-fractionations were defined as 4 to 9, 10 to 15, and >15 fractions. Radioresistant histology was defined as melanoma, renal cell carcinoma, sarcoma or spindle cell, or gastrointestinal primary.

Results: Of 4,087,967 adults with their first lifetime cancer, 90,388 (2.2%) had BM at initial diagnosis. Of these, 11,486 (12.7%) received SRS and 24,262 (26.8%) WBRT as first-course radiation therapy. The proportion of annual WBRT use decreased from 27.8% to 23.5% of newly diagnosed patients, and SRS increased from 8.7% to 17.9%. Common dose-fractionations were 30 Gy in 10 fractions (56.8%) for WBRT and 20 Gy in 1 fraction (13.0%) for SRS. On multivariate analysis, factors significantly associated with SRS versus WBRT included later year of diagnosis (2015 vs 2010, adjusted odds ratio [aOR] = 2.4), radioresistance (aOR = 2.0), academic facility (aOR = 1.9), highest income quartile (aOR = 1.6), chemotherapy administration (aOR = 1.4), and longer travel distance (>15 vs < 5 miles, aOR = 1.4). Linear regression revealed significant ExWBRT reductions (-22.4%/y, R² = 0.97, P < .001) and no significant change for ShWBRT or StWBRT. Patients were significantly more likely to receive ShWBRT than StWBRT if not treated with chemotherapy (aOR = 3.5).

Conclusions: Utilization of WBRT, particularly ExWBRT, decreased while SRS utilization doubled as the first radiation therapy course in patients with BM at diagnosis. Patients with radioresistant histologies were more likely to receive SRS. Those not receiving chemotherapy, potentially owing to poor performance status, were less likely to receive SRS and more likely to receive ShWBRT.

Figure 1

Cohort derivation. Abbreviations: BED = biologically effective dose; EBRT = external-beam radiation therapy; ExWBRT = extended-course WBRT; ShWBRT = short-course; SRS, stereotactic radiosurgery; WBRT = whole brain radiation therapy; StWBRT = standard-course WBRT.

Figure 2

Yearly trends of whole brain radiation therapy (WBRT) and stereotactic radiosurgery (SRS) for patients with their first lifetime malignancy and brain metastasis (BM) at diagnosis. The y-axis represents the percentage of patients diagnosed with BM in a year (2010, n = 14,613; 2011, n = 14,529; 2012, n = 14,665; 2013, n = 15,347; 2014, n = 15,727; 2015, n = 15,507) treated with the modality.

Figure 3

Yearly trends of whole brain radiation therapy (WBRT) dose-fractionations for patients with their first lifetime malignancy and brain metastasis (BM) at diagnosis. The y-axis represents the percentage of patients diagnosed with BM in a year (2010, n = 14,613; 2011, n = 14,529; 2012, n = 14,665; 2013, n = 15,347; 2014, n = 15,727; 2015, n = 15,507) treated with the modality. Linear regression model fits are plotted with 95% confidence intervals.