What is SBRT?

At the Austin Center for Radiation Oncology, we offer patients two types of radiation therapy: IMRT and SBRT. Let’s review these briefly.

These techniques deliver radiation from an external source which rotates around the patient. A customized plan is devised for each patient in such a way that the prescribed dose treats little beyond the cancerous tissue. Hence, only minimal parts of normal tissue get dosed. Daily imaging prior to treatment ensures faithful delivery of the planned dose. Side-effects are minimal.

IMRT stands for Intensity Modulated Radiation Therapy. It is given five days a week for up to nine weeks. IMRT has a long track-record which proves that it works remarkably well. But a prolonged schedule can be inconvenient for many patients.

SBRT stands for Stereotactic Body Radiation Therapy. It is newer but has excellent early results. Treatment can be completed in just five sessions, mostly through special maneuvers for accurate daily setup and normal tissue avoidance. National Comprehensive Cancer Network (NCCN) guidelines endorse SBRT as an alternative to IMRT for most cancers that involve only the prostate. It can also be used to treat recurrences after previous treatment.

Radiation side effects

Men can experience some side effects following IMRT or SBRT treatments. The Radiation Oncologist will discuss these during the initial consultation.

Side effects could include fatigue; irritation to the urethra and bladder; a weak urinary stream; an increased need to urinate day and night; an urgent need to urinate known as urinary urgency; increased bowel movements, soft or loose stools, diarrhea; rectal bleeding or erectile dysfunction.

Is SBRT the same as Cyberknife® ?

The short answer is ‘yes’. To be clear, Cyberknife® is a form of SBRT. In reality, the word Cyberknife® is not as much a procedure, but the name of a machine or linear accelerator that delivers radiation. At the Austin Center for Radiation Oncology, we have a Halcyon linear accelerator that is capable of delivering Stereotactic Body Radiotherapy (SBRT), with the added value of being able to visualize the organs.

Patient Case Study

A 75-year-old gentleman with early-stage prostate cancer received five treatments with SBRT. After placement of SpaceOAR gel and fiducial markers, scans such as CT and MRI imaging were done to make a customized radiation plan. This image shows the plan. The red line demarcates a focused zone of high dose to the nodule, while the entire prostate and seminal vesicles got a standard dose. What was critical to the success of this treatment was the SpaceOAR gel which protected the rectum completely from the high dose. This patient experienced no toxicity during treatment and his cancer is in remission.