Comparing Whole Brain Radiation, 1, 3, And 5 Fraction Stereotactic Radiation In Patients With Brain Metastases

Abstract

Patients with brain metastases are commonly treated with Radiation therapy (RT). Commonly used RT options include whole brain radiation (WBRT), Stereotactic radiosurgery (1 fraction, fx) or stereotactic radiation therapy (SRT, 2-5 fractions) depending on the number of lesions, primary cancer, KPS and other patient and tumor characteristics. The purpose of this study was to compare 1-year survival outcomes between WBRT, 1 fx SRS, 3 fx SRT and 5fx SRT. A retrospective analysis of 910 treatments with radiation therapy (RT) for 700 patients with brain metastases was performed (2012-2018). Treatment variables were extracted using Oncora software platform. Data for the four treatment groups (1fx, 3fx, 5fx and WBRT) was collected. Baseline characteristics between the treatment groups were compared using Chi-square test, Analysis of Variance, and the Kruskal-Wallis test. Mortality at 1 year was compared between the four treatment groups using a logistic regression model, adjusting for age, gender and KPS. Hosmer-Lemeshow test was used to determine whether the model provided a good fit. Tukey’s method was used to adjust for the multiple comparisons between the 4 treatment groups. P<0.05 was considered statistically significant. SAS 9.4 was used for the statistical analysis. Mean age (SD) was 63.3(12.3) years. Gender distribution was 397 (56.7%) females and 303 (43.3%) males. Treatment modalities were 244(34.9%) 1fx, 65(9.3%) 3fx, 14(2.0%) 5fx and 377(53.9%) whole brain (WBRT). Median 1fx dose was 20Gy, 3fx dose 24Gy and 5fx dose 30Gy and WBRT dose of 30Gy. Treatment groups were similar in term of age (p = 0.44). There were significant differences in the terms of the KPS distributions between treatments (p<0.0001), with median of 80, 80, 80 and 70 for treatments 1fx, 3fx, 5fx and WBRT, respectively although no significant gender differences were observed among the treatment groups (p = 0.44). The overall mortality rate at 1 year was 69.3%, with 136(55.7%), 42(64.6%), 8(57.1%) and 299(79.3%) for 1fx, 3fx, 5fx and WBRT, respectively. In the 6 pairwise comparisons (table1), 1fx had 62% lower odds of death compared to WBRT (OR = 0.38, 95% CI 0.23 to 0.63, p<0.0001). Age was significantly associated with mortality (OR = 1.03, 95% CI 1.02 to 1.05, p<0.0001), with 3% higher odds of 1-year mortality, for every 1-year increase in age. In women, 10 units increase of KPS had 31% lower odds of 1-year mortality (OR = 0.69, 95% CI 0.56 to 0.85, p = 0.001), while not significant in men (OR = 0.93, 95% CI 0.74 to 1.17, p = 0.56). We found that “Non-WBRT” group had 59% lower odds of 1-year mortality (OR = 0.41, 95% CI 0.28 to 0.59, p<0.0001) compared to the WB group. There was no difference in 1-year mortality in the three stereotactic protocols. Single fraction SRS had improved survival compared to WBRT at 1 year. Prospective studies are needed are needed to confirm survival and toxicity in the treatment groups.