External Radiation

Introduction

The large majority of radiotherapy is administered with high-energy X-rays (photons). Shaping of radiation fields is performed by the intersection of multiple beams from multiple angles with the objective of delivering an effective dose to the prostate while minimizing the dose that impacts other tissue. Technologies include:

• 3D Conformal Radiotherapy (3D CRT) is a method of shaping radiation fields to conform to individual patient anatomies; this works relatively well for simple geometries, e.g. spherical targets.
• Intensity-modulated radiotherapy (IMRT) is a hardware/software solution of further refining this 3D radiation shaping capability to accommodate complicated shapes, e.g. being able to adjust to concavities, convexities and various irregularities.
• Image Guided Radiotherapy (IGRT) involves the utilization of imaging technologies within treatment rooms to ensure proper placement of radiotherapy areas have been loosely termed. Therefore, IGRT and IMRT are not competing technologies, but complimentary approaches.
• Stereotactic body radiotherapy (SBRT) consists of a much shorter course of radiotherapy than the standard approach (only 5 treatment sessions as compared to the 45 for the standard course).
• Proton Beam Radiotherapy uses a beam of protons (instead of photons) which enter the body with a low radiation dose and deposit the bulk of their cancer-fighting energy right at the tumor. Proton radiation can be used as a standalone treatment or to provide a dose boost in combination with IMRT.

PCRI Resources:

• Update On Image-Guided Radiation Therapy PDF • Patrick Kupelian, MD 2011
• Intensity Modulated Radiation Therapy (IMRT) • Lisa Chaiken, MD, et al. 2004
• Nine Decisions Before Choosing Radiation Therapy After Prostatectomy PDF 2010

Related Resources:

• How Does Radiation Therapy Work? – American Society for Radiation Oncology
• External Beam Radiation therapy – American Society for Radiation Oncology
• Stereotactic Radiation therapy – American Society for Radiation Oncology
• Radiation Therapy for Prostate Cancer – A Patient Guide – UCSF
• Emerging Technologies in Prostate Cancer Radiation Therapy: Improving the Therapeutic Window – Moffitt Cancer Center

Page updated 8/1/11