Radiation oncologist Sean McBride says the best choice of radiation therapy for prostate cancer depends on each patient’s specific disease.
When it comes to treatment for prostate cancer, men now have many good options that have improved prognosis for the disease. One effective treatment is radiation therapy, either alone or in combination with other treatments, such as hormone therapy or surgery. Radiation therapy uses high levels of radiation to kill prostate cancer cells.
Yet the many different choices regarding prostate cancer radiation therapy can be hard to sort out. To help make sense of the options, we spoke with Memorial Sloan Kettering Cancer Center radiation oncologist Sean McBride.
What are the different types of radiation therapy for newly diagnosed prostate cancer?
Radiation therapy for newly diagnosed prostate cancer can be divided into two main types: brachytherapy and external beam radiation.
Brachytherapy, also known as internal radiation, can be further subdivided into low-dose rate and high-dose rate. In low-dose-rate brachytherapy, a doctor carefully places seeds containing radiation within the prostate while the patient is under anesthesia. After this relatively brief procedure, the seeds stay in the body and give off their radiation dose over several months. For high-dose-rate brachytherapy, 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. The radiation source is then removed from the body before the patient wakes up.
External beam radiation delivers the radiation from outside the body, most often in the form of x-rays but sometimes as charged particles called protons or other types of energy. External beam radiation for prostate cancer includes intensity-modulated, image-guided radiation therapy (IG-IMRT), typically delivered over five weeks, and hypofractionated radiation therapy (what we call MSK Precise ™), typically delivered over a week and a half in five total treatments.
Do we know which treatment is best for prostate cancer — brachytherapy or external beam radiation?
It’s not a question of which type of radiation therapy is best in general, but rather which therapy is best for the patient’s specific disease and quality-of-life concerns. We want to use the most tailored, pinpointed radiation to treat the prostate tumor effectively while minimizing side effects. This can depend on the tumor’s size and stage as well as other patient characteristics and even a patient’s individual preferences.
Are there side effects of the combination approach to prostate cancer radiation therapy?
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, Gleason score, extent of visible disease on magnetic resonance imaging (MRI) — we have learned over the years that higher doses of radiation are critical to achieving better results. Some evidence, including a large trial, suggests that for patients with intermediate- or high-risk prostate cancer, a combined approach using brachytherapy along with external beam radiation may be best compared to standard dose external beam radiation therapy alone.
Are there side effects of the combination approach?
There is a slightly higher chance that patients who receive the combined therapy (brachytherapy and external beam radiation) will have rectal irritation or urinary side effects. This is common with prostate cancer radiation therapy because the radiation can damage cells in the tissues surrounding the prostate. But at MSK, we routinely use sophisticated computer-based 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. We have also found that, when treating with the combined approach, using the high-dose-rate brachytherapy compared to low-dose-rate brachytherapy may have less in the way of side effects.
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 the rectum is exposed to. This leads to fewer side effects for the patient. The rectal spacer gel is biodegradable and dissolves on its own within the body after a few months.
When is brachytherapy alone the right choice?
For some patients with disease that is confined to the prostate and not too aggressive (for example, intermediate risk), brachytherapy alone is a good option. It is also convenient for the patient as it is done in an outpatient setting and most people can get back to work within a few days.
But brachytherapy is not right for everyone. For some patients with less-aggressive disease, a watch-and-wait approach would be preferred. At MSK, our philosophy is that when the disease is caught very early, it is very appropriate to do active surveillance and hold off on treatment.
This philosophy applies to patients with 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. There are also very select patients with Gleason 7 disease who may be candidates for active surveillance.
Those patients with very large prostates or those who have significant urinary problems at baseline may experience more side effects with brachytherapy. 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 best approach to avoid the urinary problems that could be associated with radiation treatments. In some cases, when the prostate is moderately enlarged, hormonal therapy can be effectively used to shrink the prostate down over several months. This can then be followed by brachytherapy or external beam radiotherapy.
What is stereotactic body radiation therapy (SBRT) and what advantages does it offer?
Stereotactic body radiation therapy, or SBRT, involves the use of sophisticated image guidance that pinpoints the exact three-dimensional location of a tumor so the radiation can be more precisely delivered to cancer cells. Traditionally, external beam radiation has been delivered in anywhere from 45-48 sessions over multiple weeks. But large, randomized studies have shown that shorter courses of radiation (20-26 sessions) are just as safe and effective. Therefore, at MSK, we have shortened all our radiation courses.
There is increasing interest in giving this radiation in very short courses of treatment using intense radiation doses, called hypofractionated radiation therapy. Many of the people we care for have a type of radiation therapy called MSK PreciseTM. This is a hypofractionated form of SBRT that can be given in five sessions. MSK has been doing this for the past 20 years, and the results in the several hundred people who’ve been treated have been excellent so far. The treatment is very well tolerated and quite effective
Because of its superior precision, MSK Precise can have fewer side effects than more conventional radiation techniques, with extremely low rates of incontinence (urinary leakage) and rectal problems. The sexual side effects are low, similar to what is experienced with more extended external radiation techniques. And of course, it’s much more convenient for patients.
What is the recovery like from prostate cancer radiation therapy?
People almost always continue to work and enjoy leisure activities during radiation. Typically, they will experience temporary, mild urinary and bowel issues that resolve a few weeks to a few months after radiation treatment is completed.
Does MSK offer proton therapy for prostate cancer?
Some men with prostate cancer may choose to receive another form of external-beam radiation therapy called proton therapy. Proton therapy can deliver a high radiation dose to the prostate while lowering the radiation dose to normal surrounding tissue. It is unclear if there is any advantage to proton therapy compared with IMRT. We are now studying how these approaches compare in terms of side effects and outcomes at the New York Proton Center. These efforts are being led by radiation oncologist Daniel Gorovets.
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. 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. We will often obtain next-generation imaging (for example, PSMA PET) and do genomic testing. 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 one of the few centers in the world to do MRI-based treatment planning and one of the few centers in the US to offer MRI-guided treatment. 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. 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.
We 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 active, 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.
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 these areas that gives us an opportunity to provide an approach that’s not one-size-fits-all but tailored to each person.
Our goal is to try to reduce the burden of therapy on our patients. If we can use our technology and expertise to combine therapies or condense the treatment from two and a half months down to sometimes as little as a week, we can eradicate our patients’ disease and preserve their quality of life.
The story originally was published October 25, 2018 and was updated April 19, 2022.
