Image-guided radiotherapy for prostate cancer using 3 different techniques: localization data of 186 patients

Area of Science:

• Radiation Oncology
• Medical Imaging
• Prostate Cancer Treatment

Background:

• Image-guided radiotherapy (IGRT) is crucial for precise cancer treatment.
• Accurate localization of the prostate gland is essential to minimize radiation dose to surrounding healthy tissues.
• Evaluating different imaging modalities is key to optimizing IGRT protocols.

Purpose of the Study:

• To compare ultrasound (US), stereoscopic X-ray imaging (X-ray), and kV cone-beam computed tomography (CBCT) for assessing interfraction and intrafraction localization errors in prostate cancer radiotherapy.
• To determine the effectiveness of these techniques in reducing planning target volume (PTV) margins.

Main Methods:

• A hypofractionated protocol delivering 70.2 Gy in 26 fractions using conformal dynamic arcs was used.
• 186 prostate cancer patients were treated using X-ray (32), CBCT (30), or US (124).
• Interfraction and intrafraction prostate motion, including translations and rotations, were analyzed.

Main Results:

• Stereoscopic X-ray imaging demonstrated the lowest systematic and random errors in prostate localization compared to CBCT and US.
• Residual errors with X-ray were consistently below 1 mm in all directions.
• Intrafraction prostate motion was minimal, generally less than 1 mm in all directions.

Conclusions:

• Daily on-line IGRT with stereoscopic X-ray imaging significantly reduces PTV margins by accounting for interfraction errors and intrafraction motion.
• X-ray imaging presents the optimal combination of accuracy, reliability, patient dose, and time efficiency for daily prostate IGRT.
• This approach facilitates potential dose escalation in prostate cancer treatment.