We spoke with MSK radiation oncologist Michael Zelefsky to get the scoop on the latest radiation treatments for prostate cancer.
When it comes to treatment for prostate cancer, men now have several good options. Advances in surgery, radiation, and endocrine therapy have greatly improved the prognosis for patients with this disease. Yet the many different choices — including the various types of radiation therapy — can be hard to sort out.
To help make sense of the options, we spoke with Michael Zelefsky, Vice Chair of Memorial Sloan Kettering’s Department of Radiation Oncology.
What are the different types of radiation therapy for prostate cancer?
Brachytherapy can be further subdivided into low dose rate and high dose rate. In low-dose-rate brachytherapy, seeds containing radiation are carefully placed within the prostate while the patient is under anesthesia. The seeds stay in the body and give off their radiation dose over a period of several months. For high-dose-rate brachytherapy, tubes or catheters are placed into the prostate, also while the patient is under anesthesia, and a high dose of radiation is delivered over a few minutes, often in several sessions. The radiation source is then removed from the body.Back to top
Do we know which treatment is better for prostate cancer, brachytherapy or external beam radiation?
It’s not a question of which therapy is better but rather which therapy is the most tailored, pinpointed radiation for the patient’s specific disease.
When it comes to early stages of disease, patients very frequently do well with either brachytherapy or external beam radiation. Success rates of around 90% or higher can be achieved with either approach. When the disease is somewhat more advanced — based on the PSA level or the Gleason score or visible evidence of disease on an MRI — we have learned over the years that higher doses of radiation are critical to achieving better results. Some evidence suggests that for patients with intermediate- or high-risk prostate cancer, a combined approach using brachytherapy along with external beam radiation may be best.
Data that we have published recently show that for patients with intermediate-risk disease, the combination of external beam radiation with brachytherapy not only provides better biochemical control, in terms of PSA level, but also reduces the risk of distant metastases, or spread of the disease. Another recent study from Canada, which compared outcomes in patients who were treated with external beam radiation or a combination approach, found superior results when the combined approach was used. These studies provide strong evidence that higher doses of radiation provide an important benefit to patients with intermediate-risk and high-risk prostate cancers.Back to top
Are there side effects of the combination approach?
There is a slightly higher chance that patients who receive the combined therapy will have rectal irritation or urinary side effects, both of which are common with any radiation treatment given to the prostate. But at MSK, we routinely use sophisticated planning techniques that help us reduce the dose given to normal tissues such as the rectum, bladder, and urethra, lessening the chances of side effects and complications.
In addition, at MSK, we routinely use a rectal spacer gel, which we inject between the prostate and the rectum while the patient is under mild anesthesia, to create a buffer between these two tissues. By creating this space, we can further reduce the dose of radiation that the rectum is exposed to. This leads to fewer side effects for the patient. The rectal spacer gel is biodegradable and after a few months dissolves on its own within the body, causing no harm or long-term effects.Back to top
When is brachytherapy alone the right choice?
For a patient with disease that is confined to the prostate and not too aggressive, brachytherapy alone is a good option. With the use of sophisticated real-time computer-based planning, we can use brachytherapy to deliver radiation in an extraordinarily precise way, with minimal exposure to the surrounding normal tissues. It is also convenient for the patient as it is done in an outpatient setting and most people are able to get back to work the next day.
But brachytherapy is not right for everyone. For some patients with less-aggressive disease, a watch-and-wait approach would also be very reasonable. At MSK, our philosophy is that when the disease is caught very early — meaning a low PSA level, or nonaggressive disease as reflected by a Gleason score of 6 with evidence of cancer in only a few of the biopsy samples and no evidence from the MRI of a significant amount of disease — then it would be very appropriate to do active surveillance and hold off on treatment.
Those patients with very large prostates or those who have a significant amount of urinary symptoms may experience more side effects with brachytherapy. In these situations, we often steer such patients toward other kinds of treatment such as surgery or external beam radiotherapy. Surgery to remove a large prostate may be the better approach, to avoid the urinary symptoms that could be associated with radiation treatments. In some cases, where the prostate is moderately enlarged, hormonal therapy can be effectively used to shrink the prostate down over a period of several months. This can then be followed by brachytherapy or external beam radiotherapy.Back to top
What is stereotactic body radiation therapy (SBRT) and what advantages does it offer?
Traditionally, we deliver external beam radiation in 45 to 48 sessions over a span of ten weeks, using very sophisticated computer-based planning and enhanced imaging techniques and tumor tracking during the treatment. This is called image-guided IMRT and it is the current standard of care.
But there is increasing interest in giving this radiation in shorter courses of treatment. What we call SHARP — which stands for Stereotactic Hyperfractionated Accelerated Radiation Therapy to the Prostate — is a form of SBRT that can be given in five sessions instead of the usual 45 to 48. We have been doing this for the last seven years here, and the results in the several hundred patients that we’ve treated have so far been excellent. The treatment is very well tolerated, with outcomes that are at least equivalent to and possibly better than the standard ten weeks of treatment. And of course it’s much more convenient for the patient.
The SHARP program here at MSK is not simply short-course, high-dose treatment. It takes advantage of innovations in planning, imaging, and mapping to enhance the precision and safety of the treatment. It includes MRI-based planning, in which the mapping of therapy is accomplished only with MRI and not CT scanning — something we are the only ones in the world to do at this time. We also use what are called fiducial markers, placed in the prostate, to track the location of the prostate before and during the treatment. And, as I said, we use a rectal spacer gel that gives us an opportunity to move the rectum out of the way of the high doses of treatment.
For patients with more-advanced tumors, we are completing a phase II trial in which we’re combining sophisticated brachytherapy approaches with SHARP. This kind of combination of dose-intense or escalated radiation may end up being a very effective regimen.
We’ll soon be rolling out a new program in which, in selected patients, we will use SHARP to intensify radiation doses to portions of the prostate while at the same time significantly reducing doses to normal tissues such as the bladder neck region next to the prostate, the nerves and blood vessels controlling erectile function, and the rectum. This is really novel — a new paradigm, really, in radiation therapy. It requires a great deal of collaboration with our medical physics team to try to get the most accurate positioning of the prostate during the actual three or four minutes of the treatment.Back to top
What should patients know about MSK’s approach to treating prostate cancer?
At MSK, we manage prostate cancer in a very comprehensive way, tailored to each patient’s disease and to the individual person. There is no one specific therapy that is best for everyone.
Our initial assessment includes a carefully evaluated biopsy and a very detailed MRI to show the location of the disease, the integrity or soundness of the capsule surrounding the prostate, and the amount of disease. Then, based on that information — and with input from the urologist, the radiation oncologist, and the medical oncologist — we can provide a comprehensive recommendation.
The radiotherapy we do here at MSK is state-of-the-art and unparalleled. We are the only center in the world to do MRI-based treatment planning. When we give brachytherapy, we use computer software that provides us with real-time information about the quality and accuracy of the seed implant during the procedure. This allows us to make adjustments while the patient is still under anesthesia, so that when the procedure is completed, we have been able to achieve ideal placement of the radiation seeds. This translates into improved outcomes.
For more advanced disease, we have ongoing studies in which we combine novel hormonal therapy agents with radiation to achieve better results. Even the way we follow our patients after treatment is unique, with carefully sequenced MRI checks that give us opportunities to monitor patients extremely closely.Back to top
So we do it all….
Yes, that’s the unique part of our program — we have expertise in multiple areas of prostate cancer radiotherapy management. Some places just focus on external radiation alone. Some just do seed implants. Other centers do combined therapies for everybody. It’s our expertise in all of these areas that gives us an opportunity to provide an approach that’s not one-size-fits-all, but tailored to the individual.
The thrust of our approach is to try to reduce the burden of therapy on our patients. And if we can utilize the most sophisticated technologies and innovations in radiotherapy to condense the radiotherapy program from sometimes two and a half months down to a week, or to combine some of these therapies, we can provide added benefit and value for our patients.Back to top