From an interview with Virginia Clyburn-Ipock, MD McLeod Radiation Therapy
Today’s radiation therapy for cancer uses computerized, multiple streams of highly focused beams to improve survival, reduce side effects and reduce the number of treatments needed.
Here are key points from Dr. Clyburn-Ipock’s comments:
The technological advances in radiation therapy over the last 10 years have been remarkable. One of our biggest challenges as radiation oncologists is trying to inform the patient that the radiation we use now is not the same radiation that their grandfather had 20 or 30 years ago. The technological advancements are very remarkable.
One of the first things that has come out that has really changed radiation is IMRT or intensity modulated radiotherapy. What it allows us to do is to deliver a very conformal dose of radiation to our tumor volume. And it allows us to give a very high dose of radiation to that area, while there is drop off of radiation near normal structures that we want to avoid. We can accomplish this by using multiple beam targets surrounding the patient and every beam has a beam’s eye view of the target. We can shape how that beam is formed as it is passing through the body and hitting the target.
When you use more beams around the patient, each beam carries less dose. Therefore, the area it’s passing through – the normal structures of the body – are actually getting less of a dose than it used to “back in the day” when we would use just a few large fields to treat an area.
IMRT, which delivers a very conformed dose of radiation to our target while delivering less radiation to surrounding organs, is frequently used for prostate cancer, which is one of the most common cancers we see. Primarily, all of our prostate cancer patients will be treated with IMRT, because it allows us to give a large dose of radiation to the prostate and decrease the dose to the normal structures nearby. This includes the bladder, the rectum, the femoral heads and the small bowel. Depending on the patient’s anatomy all of those organs can be near the area we are trying to target. In addition, IMRT has been shown to be very advantageous in prostate cancer in reducing long-term side effects.
The most recent advancement is called SBRT, which stands for Stereotactic Body RadioTherapy. We will commonly use this for an early-stage lung cancer. SBRT gives a very high dose of radiation in a very few treatment “fractions.” A fraction is simply a “day’s worth of radiation.” So, one fraction equals one treatment of radiation.
Traditionally, when we would treat lung cancer, patients would receive 6 to 7 weeks of radiation, with the radiation delivered every day, five days a week.
If a patient has a small lung tumor, and it has a certain cell histology, we can also use SBRT. This allows us to give large doses of radiation in just a few treatments. The radiation can also be delivered in as few as five or even 3 treatments.
You can see how this is much easier on the patient – having to come in 5 times or 3 times versus 30 times.
Unfortunately, not all patients are candidates. It has to be an early-stage lung tumor, for example.
SBRT is also used in treating certain lesions of the spine and the liver.
Advances have also been made in treating brain metastases. Previously, we would have only one basic option, which was whole-brain radiation. This would involve treating the entirety of the brain, usually over 2 to 3 weeks of radiation with anywhere from 10 to 15 treatments.
Currently, we have state-of-the-art techniques here at McLeod that allow us to deliver what is called Stereotactic RadioSurgery or SRS. We can pinpoint lesions in the brain with millimeter accuracy and deliver a very large dose of radiation in one treatment. This dose of radiation is essentially an “ablative” dose. It hits the tumor with a high enough dose of radiation that the tumor dies on the spot.
We can use this type of radiation for certain people with brain metastases that have a very good “performance status,” meaning we expect them to do very well with treatment and they have one or just a few small lesions which we can pinpoint with SRS.