Patterns of care and survival outcomes of palliative radiation for prostate cancer with bone metastases: comparison of ≤5 fractions to ≥10 fractions.

Abstract

To review the palliative radiation fractionation regimens, trends and survival of men within the National Cancer Database (NCDB) diagnosed with prostate cancer and bony metastases. A total of 3,871 patients from the NCDB were included in the analysis (patients treated from 2004-2012). The following fractionation regimens were analyzed [8 Gy × 1, 4 Gy × 5 (short course radiation therapy)], were compared to 3 Gy × 10, 2.50 Gy × 14-15 and 2 Gy × 20-30 (long course radiation therapy). Descriptive statistics, multivariable logistic regression and multivariable cox regression analysis were utilized to assess the data. Longer fractionation schemes were used for 91.7% of patients. Treatment at an academic center (OR, 2.93), increasing distance from treatment center (OR, 1.48-1.59), treatment to the ribs (OR, 2.47), and year of diagnosis 2009 or later (OR, 2.31-3.26) were associated with an increased likelihood of receiving short course radiation, while treatment to the spine (OR, 0.34) was associated with a decreased likelihood of short course radiation. On multivariable analysis, longer course of radiation was associated with increased overall survival (HR =0.66; 95% CI: 0.56-0.78, P<0.001.). However, on landmark analysis this difference disappeared once limiting the survival analysis to men who survived ≥18 months [HR =0.83; 95% CI: 0.62-1.11, P=0.21]. Fractionation schemes of ≥10 treatments remain the dominant palliative course of radiation therapy offered for metastatic prostate cancer. However, utilization of ≤5 fractions is slowly increasing, particularly at academic centers.