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SBRT for Prostate Cancer
Stereotactic Body Radiotherapy for Prostate Cancer
| The New War on Cancer | ||
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The UCLA Department of Radiation Oncology is one of the first centers in the nation to offer SBRT for prostate cancer.
Dr. Chris King is one of the leading experts in SBRT for prostate cancer at UCLA. Men with localized disease can now complete radiation in just two weeks, with no surgery. Stereotactic body radiation therapy (SBRT) delivers high doses of radiation to targeted areas in just five sessions on alternate days. This modality complements our existing treatment regimens including external beam and brachytherapy both low dose and high dose rate (HDR). Please ask your doctor if SBRT is appropriate for you. |
Overview of Contents
- What is SBRT?
- Diagnosis & Workup of Prostate Cancer
- Choosing SBRT as a Treatment
- SBRT Treatment Planning
- Results of SBRT
- Side Effects of SBRT
- Follow-up Care after SBRT
- Publications on SBRT
- Contact Us
- Educational Information
1. What is Stereotactic Body Radiotherapy (SBRT)?
UCLA was the first in the US to use of focal high dose radiotherapy to eradicate tumors over 25 years ago, and one of the pioneers in the development of linear accelerators used to deliver stereotactic radiosurgery (3-dimensional image-guided focal radiation) to ablate tumors in the brain. Today, UCLA Radiation Oncologists continue to be leaders in the use of state of the art radiation technologies for the treatment of cancer. UCLA physicians are the first in the world to have pioneered the use of stereotactic radiosurgery techniques for the treatment of prostate cancer and were the first to publish results from this treatment approach. UCLA now has an active clinical program using stereotactic body radiotherapy (abbreviated SBRT) to treat prostate cancer.
2. Diagnosis & Workup of Prostate Cancer
Prostate cancer usually presents without specific symptoms. Parts of the posterior prostate gland can be felt by a digital rectal examination (DRE) and the presence of a tumor nodule, if present, may be detected. However, the most common event that leads men to an early diagnosis of prostate cancer is through a blood test, the PSA. PSA (prostate specific antigen) is a protein that is produced by the normal prostate gland, but is also by prostate cancer tumors. It is generally elevated and progressively rising among men with prostate cancer, above what is considered a normal PSA level (less than about 4 ng/mL). The PSA level and the rate at which it increases can be used to assess the aggressiveness of the cancer and its likelihood of having possibly spread.
Read more about diagnosis and workup of prostate cancer >>
3. Choosing SBRT as a Treatment
Your doctor at UCLA will review all of the treatment options with you, comparing the pros and cons of each in great detail. Often, there will be several equally good options, and together with your doctors you will be guided through the decision making process in order to arrive at a treatment that is the most appropriate for you and that you feel most comfortable with.
Patients considered eligible and potential good candidates for prostate SBRT include those with low and intermediate risk prostate cancer (as described above).
There are many good reasons to consider and choose SBRT over the other potential options, including:
- It is entirely non-invasive (unlike brachytherapy for example, it does not involve the insertion of needles, risks of bleeding, risks of infection, general anesthesia, hospital stays, or wearing a catheter).
- It is a very short treatment course (unlike conventional external beam which takes a total of 9 weeks of daily treatments, 5 days a week) SBRT consists of a total of only 5 treatment sessions, each taking less than 15 minutes to complete, all done as an outpatient.
- The cancer control rates of SBRT are equivalent to those of brachytherapy, conventional external beam radiotherapy, or surgery.
- Sparing of radiation exposure to the rectum and bladder is equal to or better than with brachytherapy.
- The side effects are less than those experienced with brachytherapy or conventional external beam radiotherapy. Unlike surgery, there is no risk of urinary incontinence.
4. SBRT Treatment Planning
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). The delivery of SBRT is accomplished with the use of image-guidance (IGRT) via 3 implanted gold seed markers in the prostate gland. This image-guidance is integrated with an intensity modulated beam that is shaped to exactly fit and surround the prostate gland, aiming at the prostate gland continuously as the gantry rotates around the patient. This specialized state of the art beam is called RapidArc. A dedicated treatment machine, the Novalis Tx, is used to accomplish this.
Only with the use of state-of-the art image-guidance and RapidArc can the delivery of higher radiotherapy doses be done more safely than with any other technique, which translates into better cure rates and fewer side effects. With such accurate treatment delivery technology, the margin around and beyond the prostate gland that needs to be covered has been greatly reduced, thus sparing the rectum and bladder from exposure.
We currently use very small margins around the prostate gland of 3-4 mm. We prescribe a dose of 800 cGy per treatment fraction, and our total dose is 800 x 5 = 4000 cGy. Gy is the unit of radiation dose, and stands for Gray, the name of the radiation physicist. It used to be called ‘rads’. One rad is equal to one centi-Gray (cGy, or 1/100th of a Gray). Thus it takes 100 rads to make one Gray.
Figure Gold seeds (fiducials): Solid gold markers, also called fiducials, are placed by the Urologists under ultrasound guidance (just like the biopsies). These can then be imaged with stereoscopic x-rays images, and an accurate 3-dimensional position determined instantly. These seeds are an essential component in order to provide image-guidance and to correct for target positioning during treatment delivery.
Figure Novalis Tx: The Novalis Tx linear accelerator, also called LINAC (the large rotating gantry left of center) is shown illustrating how a prostate patient would be set up for treatment. High energy (megavoltage) treatment x-rays are generated by the LINAC.
The gantry rotates around the target while modulating the beam profile in order to deliver dose to the target while at the same time sparing normal organs and tissues. The image-guidance system is also shown (the x-ray tubes located in the floor and the detectors near the ceiling) and is able to automatically detect the gold seeds (fiducials) and correct for position and movement.
Figure SBRT: SBRT (stereotactic body radiotherapy) treatment plan shown with the axial, sagittal and coronal views. Note how well the bladder and rectum can be spared with the technique of RapidArc using the Novalis Tx. Dose distribution is represented by dose level color wash (red color indicating the 100% dose levels, and the blue indicating the 50% dose levels).
The Dose Volume Histogram, or DVH (upper right hand panel graph) shows how well the prostate gland is covered by 100% of the prescribed dose, while the organs at risk (rectum with orange line, bladder with yellow line, left and right femoral heads with green and red lines) are greatly spared from high doses. At a dose level of 50% of the prescribed dose, less than 25% of the rectum and bladder are exposed. At a dose level of 80% of the prescription dose, less than 10% of the bladder and rectum are exposed.
5. Results with Prostate SBRT
Our experience shows that this is a very safe approach, and one that spares the rectum and bladder to a degree not seen with other radiotherapy techniques. Dr. King began using SBRT for prostate cancer in 2003 and was one of the first in the world to do so. He has also been the first to publish results of his clinical program. In 2010 he published an update of his clinical SBRT trial, now with 2.7 years median follow-up, where he has shown that the late side effects are minimal, similar in nature as those described for standard external beam radiotherapy, and often less frequent than seen with the standard radiotherapy courses.
6. Side Effects of SBRT
No patient has experienced complete urinary obstruction or urinary incontinence, and there were no severe (grade 4) complications. Mild (grade 2) urinary and rectal side effects were rare, 5% and 2%, respectively. Moderate (grade 3) urinary and rectal side effects were also infrequent, 3.5% and 0%, respectively. These rates of mild and moderate side effects are less than those observed in published series that use modern 3-dimensional conformal techniques and dose escalated standard external beam radiotherapy. The prostate cancer control rates at 5-years with SBRT is 94%.
7. Follow-up Care after SBRT
After treatment, we will instruct you regarding care for any potential side effects. You will have follow-up in our SBRT clinics in order to assess treatment response, monitor and treat any and all delayed side-effects, as well as receive recommendation regarding any future potentially beneficial treatments. What to expect after SBRT treatments >>
8. Publications on SBRT
SBRT has been used for many localized tumors (up to 6-7 cm), or a few tumors (up to 3-5 usually) throughout the whole body. The list of tumors that has been treated successfully at UCLA and throughout the world with SBRT continues to grow. Read more >>
9. Contact Us
UCLA Health System, Department of Radiation Oncology
200 UCLA Medical Plaza, Suite B265
Los Angeles, CA 90095-6951 , Tel: (310) 825-9775 Contact Us >>
