RADIATION THERAPY

Dr. Brian Larson (Radiation Oncologist)

IMRT and IGRT in the treatment of prostate cancer: state of the art radiation treatment at Urology Centers of Alabama

One of the more exciting developments over the past year at the Urology Centers of Alabama has been the addition of Radiotherapy to the treatment options offered to patients with Prostate Cancer and other malignancies.  The construction of the Radiation Oncology department - The Van Scott Cancer Center – at the Homewood office has been the culmination of much effort on the part of the Urologists and Dr. Brian Larson, a Radiation Oncologist.  Dr Larson has worked the past 16 years in Birmingham at BMC Montclair (Trinity Medical Center) and BMC Princeton, as well as Medical Center East. 

By bringing state of the art equipment including a new top-of-the line Varian Linear Accelerator, as well as the latest in computer planning and treatment techniques to the new facility, we are able to provide treatment for prostate cancer that is second to none. 

Radiation treatment for prostate cancer is one of the major treatment options available for patients.  The advantages of radiation include avoidance of major surgery, including the required hospitalization, anesthesia, and post-operative recovery period of surgery.   Radiation treatment for prostate cancer has been used successfully for decades, but recent advances in technology have allowed an increase in the safe radiation dose achievable to the prostate, while minimizing the radiation effects on the normal tissues, such as the bladder, rectum, and pelvic bones.  This allows an improvement in cancer control, while reducing the side effects of the radiation treatments. 

Who will be involved in this procedure?

Our facility relies on a specially trained team for IMRT delivery. This team includes the radiation oncologist, medical radiation physicist, dosimetrist, radiation therapist and radiation therapy nurse.

The radiation oncologist, a specially trained physician who heads the treatment team, sets an individualized course of treatment with the help of the radiation physicist, who ensures the linear accelerator delivers the precise radiation dose and that computerized dose calculations are accurate. A dosimetrist, under the supervision of the medical radiation physicist, calculates the IMRT exposures and beam configurations necessary to deliver the dose prescribed by the radiation oncologist. Highly trained radiation therapists position the patient on the treatment table and operate the machine. The radiation therapy nurse provides the patient with information about the treatment and possible adverse reactions.

What equipment is used?

A medical linear accelerator generates the photons, or x-rays, used in IMRT. The machine is the size of a small room—approximately 10 feet high and 15 feet long. The patient lies on the treatment table, while the linear accelerator delivers beams of radiation to the tumor from various directions. The intensity of each beam's radiation dose is dynamically varied according to treatment plan.

How does IMRT work?

IMRT represents an evolution of radiation technology, from standard to 3D to IMRT. The evolution in technology offers the possibility of better cure rates with fewer side effects.

1. Standard radiation involved starting with plain x-rays of the pelvis. Lines were hand drawn on each x-ray film to make "radiation fields". Lead blocks were then created which matched the hand drawings. Usually, four radiation beams were used, entering the body from the front, back, and both sides.
2. 3D-conformal radiation involved starting with a CT scan. The prostate, rectum, and bladder were circled on a computer screen which showed the CT images. Any number of radiation beams could be used, and the computer shaped the beams to precisely match the contour of the prostate. Beams could be angled so that they missed most of the bladder and rectum, but passed through the prostate.
3. IMRT is even more computer intensive than 3D. Every beam is broken down into tiny "beamlets", and each beamlet can be given a different dose. This results in beams with different intensities across their surfaces. Multiple beams are used for each treatment. Although the beams are all different in shape and intensity profiles, once they all converge on the prostate you are left with a high dose covering the prostate gland, and a lower dose hitting the normal tissues, such as rectum and bladder.

Studies consistently show that the higher the radiation dose is, the better the chance of curing prostate cancer. A radiation dose of 66 Gray (Gy) will result in a 65% chance of being cancer-free at five years, but a dose of 80 Gy may result in a 90% chance, for early stage cancer. The possibility of rectal damage has prevented radiation oncologists from using high dosages of radiation in the past. Now, with IMRT, giving doses approaching 80 Gy has become safer and more common.  

IGRT - Image Guided Radiation Therapy

IGRT is an advanced technology that allows radiation to be delivered to tumors with more precision than was traditionally possible. One of the challenges encountered when radiation is delivered to a tumor is that the tumor can move based on the patient's day to day position on the treatment table, as well as internal organ motion. IGRT uses advanced imaging technology with on-board imaging (OBI). This OBI uses radiation beams with diagnostic x-ray energies in order to optimize the quality of the x-ray image and allow the radiation oncologist to visualize a patient's anatomy such as pelvic bones or implanted markers, with each radiation treatment. The Urology Centers of Alabama physicians use a special technique to insert fiducial markers into the prostate for Image Guided Radiation Therapy. This technique can be performed on an outpatient basis in the radiation oncology facility.

This added accuracy allows radiation to be delivered to a tumor based on its location in the body at the precise moment of treatment.  Thus IGRT allows the precise delivery of radiation to tumors in real time while allowing normal tissues to receive minimal radiation.

IGRT sets the stage for allowing the radiation oncologist to safely increase the radiation dose to tumors while minimizing side effects. The potential for IGRT to result in increased tumor control and cure is unparalleled.