Percent of remaining life on palliative radiation treatment: solely a function of fractionation?

Background This study analyzed the percent of remaining life (PRL) on treatment in patients irradiated for bone metastases. Bone metastases were treated together with other target volumes, if indicated, e.g. a 10-fraction treatment course that included brain and bone metastases. PRL was determined by calculating the time between start and finish of palliative radiotherapy (minimum 1 day in case of a single-fraction regimen) and dividing it by overall survival in days from start of radiotherapy. Materials and methods Different baseline parameters were assessed for association with dichotomized PRL (< 5% vs. ≥ 5%). The retrospective study included 219 patients (287 courses of palliative radiotherapy). After univariate analyses, multi-nominal logistic regression was employed. Results PRL on treatment ranged from 1–23%. Single-fraction radiotherapy resulted in < 5% PRL on treatment in all cases. All courses with 10 fractions resulted in at least 5% PRL on treatment. Significant associations were found between various baseline parameters and PRL category. With fractionation included in the regression model, 3 parameters retained significant p-values: Karnofsky performance status (KPS), none-bone target volume and fractionation (all with p < 0.001). If analyzed without fractionation, none-bone target volume (p < 0.001), hemoglobin (p < 0.001), KPS (p = 0.01), lack of additional systemic treatment (p = 0.01), and hypercalcemia (p = 0.04) were significant. Conclusions Fractionation is an easily modifiable factor with high impact on PRL. Patients with KPS < 70 and those treated for additional target types during the same course are at high risk of spending a larger proportion of their remaining life on treatment.