IMRT ‘Takes Precision to the Next Level’ in Prostate Cancer Radiation

Intensity-modulated radiation therapy (IMRT) — which is a common radiation strategy for men with prostate cancer — has changed and improved over the last two decades. The treatment is now more precise than ever, according to a review published in Translational Andrology and Urology.

This therapy can help doctors carefully avoid radiating organs near the prostate.

CURE® recently spoke with Dr. Arun Goel, site chief of genitourinary radiation oncology at the Perelman Center for Advanced Medicine at the University of Pennsylvania about what IMRT is, what it means for patients, what they can expect before receiving this treatment and more.

CURE®: What is IMRT and what does it mean for patients with prostate cancer?

Goel: [IMRT] generally refers to an advanced form of photon-based radiation therapy. If you look at IMRT plans, we typically result in very high doses of radiation to the prostate, while minimizing dose to organs like the bladder, rectum, bowel or even the bony structures.

Generally, the total dose is delivered across five to nine weeks in small daily doses. There's something called 3D conformal radiation therapy. We basically use a computed tomography (CT; a machine that captures detailed images of the areas in the body) scan to get a three-dimensional model of the target the organs that are around the target, in this case, the prostate.

That information is then used to shape three or four radiation beams to cover the tumor. When using that approach, we get great coverage of the prostate, but you also would get a more-than-necessary dose to other organs. That technique is still used for a variety of cancers because generally, with those types of cancers, we give lower dose of radiation. With prostate cancer, we have to give higher doses of radiation to actually achieve cure. So what IMRT does is it really takes precision to the next level. It divides the radiation beams into smaller beamlets, or even arcs, in which the radiation is delivered as the machine rotates around the patient. The intensity of the beam varies depending on the angle the beam or position in the ark and that allows us to sculpt the dose around adjacent organs.

For patients who have been told that they are going to receive IMRT, what can they expect?

It'll vary from place to place. In certain practices, there may be a small outpatient procedure where some markers are placed into the prostate both markers, or a rectal spacer or gel, which is an instrument that pushes the prostate away from the rectum, allowing the [clinicians] to reduce rectal dose.

Afterwards, there's something called a simulation or a planning scan. Essentially, it's basically just a CAT scan, maybe an MRI. And patients are generally given some sort of preparation leading up to it. It may be just to increase your hydration, there may be a bowel preparation— probably less so than you do for a colonoscopy — but some sort of prep just to empty the bowels before you come in. The CAT scan is performed of the patient in the treatment position, which may involve the patient having to keep a full bladder for a short amount of time. This is generally performed by a set of radiation therapists under the guidance of a physician.

At simulation, patients may also get some small pinpoint tattoos. And after that, there's usually some downtime as the plans are being generated. The next time, they may show up maybe one to two weeks later to start their daily treatments.

What are some side effects patients may experience after IMRT?

Side effects generally involve some short-term fatigue or changes in urinary or bowel functions. Inflammation of the bladder and inflammation of the urethra can lead to increase urinary frequency, some urinary urgency, a weakening of the urinary stream or even some burning with urination. Inflammation of the rectal wall can lead to diarrhea or pain when defecating.

It's important to say that these side effects are generally in the mild category and temporary, meaning that they can be managed with either lifestyle modifications, pretty routine over the counter prescription medications and they should resolve within eight to 12 weeks after radiation therapy is completed.

READ MORE: Initial Quality of Life Decreases After Radiation in Prostate Cancer

It's also important to remember that experiences are going to vary from patient to patient. For a small number of patients, these bothersome urinary or bowel complaints, or side effects that require management with medications actually can become persistent or rise episodically over the course of many years. Generally, that number is going to be around 10%. More major side effects with radiation therapy are pretty rare.

Sexual side effects can also be challenging to tease out. A lot of studies are going to include a wide variety of men, different ages, different baseline sexual function. Generally, there's no immediate impact on sexual function with radiation therapy, but it may

accelerate an actual age-related decline. So, when we look at men who have good sexual function at baseline, meaning that they're able to successfully have sex and 50% of them will still be able to at five years. There can be some variability if there's use of hormone therapy, which is probably out of scope for this but certainly something that's worth talking to physicians about.

This transcription was edited for clarity and conciseness.

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