Plan quality and dosimetric association of patient-reported rectal and urinary toxicities for prostate stereotactic body radiotherapy

To study the association between dosimetric parameters with patient-reported quality-of-life (QOL) in urinary irritative/incontinency and bowel functions for prostate stereotactic body radiotherapy (SBRT).

The patient-reported QOL was evaluated using the Expanded Prostate Cancer Index Composite (EPIC-26). According to the progression in QOL score over 12months, patients were assigned to one of three subgroups: score decrement, no change, or increment. The dosimetric parameters were cross-compared among subgroups in urinary and bowel domains using univariate Analysis of Variance (ANOVA). The evaluated dosimetric metrics included target volume, V100 (volume receiving 100% prescription dose); rectal volume/dose-volume endpoints, maximum/mean doses; bladder volume/dose-volume endpoints, and maximum/mean doses.

Patients with consistent QOL reduction in urinary irritation function were significantly associated with greater mean bladder dose, greater V85/V90/V95/V100 and D2cc/D10cc. Patients with QOL reduction in urinary incontinence were marginally associated with greater mean bladder dose (p=0.06). None of the evaluated dosimetric parameters showed a significant correlation with QOL score change in bowel function.

Patients with large prostate size were more susceptible to QOL decrements for urinary irritative and incontinency functions. Large bladder V85/V90/V95/V100 was associated with QOL decrements in the urinary irritative domain at 1-year after prostate SBRT.

Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology. 2016 Aug 29 [Epub ahead of print]

X Sharon Qi, Jason P Wang, Caitlin L Gomez, Weber Shao, Xiaoqing Xu, Christopher King, Daniel A Low, Michael Steinberg, Patrick Kupelian

Department of Radiation Oncology, University of California Los Angeles School of Medicine, USA. Electronic address: ., Department of Radiation Oncology, University of California Los Angeles School of Medicine, USA.