Dosimetric and clinical impact of 3D vs. 2D planning in palliative radiotherapy for bone metastases.

Purpose: The incorporation of three-dimensional (3D) planning for the treatment of bone metastases has been embraced in many North American practices with assumed superior tumor targeting, sparing of normal structures, and improvement in patient outcomes. The goal of our project was to evaluate the dosimetric and clinical impact of 3D vs. two-dimensional (2D) planning for patients who require simple palliative radiotherapy techniques (≤ 2 beams) for bone metastases.

Methods: Patients undergoing palliative radiation therapy for bone metastases were eligible. The study oncologists first documented the intended treatment target, defined the treatment target/field using digital radiographs (2D), followed by using full 3D planning computerized tomography volumetric datasets. Treatment plans were compared dosimetrically, and patient-reported outcomes (pain, fatigue, anorexia, and nausea) were compared against a historical cohort treated with 2D plans.

Results: Eighty-five patients were enrolled in the study group. Review of the 3D datasets led to changes in the target area of interest in 44/85 (52 %) of cases, of which 21/85 (25 %) were clinically significant. 3D plans resulted in superior target coverage and normal tissue sparing. There was no significant difference in patient-reported outcomes however.

Conclusion: 3D radiotherapy planning resulted in superior treatment plans but we were unable to demonstrate a significant benefit in clinical outcomes. Prospective study designs are needed to describe the contemporary expectation of palliative radiotherapy for bone metastases in the modern era of 3D planning.