Abstract
Adaptive image-guided intensity-modulated radiation therapy (IG-IMRT) is a perspective method for the treatment of localized prostate cancer. Validate optimal protocols for IG-IMRT using kilovoltage cone-beam CT (CBCT) are required.
Seventy-six patients with prostate cancer were treated using adaptive IG-IMRT. Based on the CBCT performed during the first 10 fractions of radiotherapy, an average prostate position in relation to the pelvic bones was determined in antero-posterior AP, supero-inferior SI, and right-left axes.
An adapted treatment plan for the second phase of the treatment included an isocenter shift into its average position (correction of the systematic error Σ). A margin between a clinical and planned target volume (CTV-PTV) was adjusted according to the magnitude of random error σ.
During the second phase of radiotherapy, set-up of patients was performed daily on pelvic bones using kilovoltage skiagraphic imaging in two projections (kV-kV). Follow-up CBCTs were repeated once a week.
IG-IMRT protocol integrating CBCT and kV-kV imaging provided adequate coverage of the target volume and proved to be compatible with departmental workflow. Margin reduction around the CTV is a prerequisite for dose escalation aimed at a intraprostatic lesion.