MRI-Guided Radiation a ‘Very Important’ Advancement in Prostate Cancer Treatment

“In terms of radiation oncology, our field seems like it’s changing every year with advancements in technology,” Dr. Matthew Solhjem said.

Dr. Matthew Solhjem, a radiation oncologist with Providence Cancer Institute and The Oregon Clinic, both in Portland, knows how rapidly things can change.

“In terms of radiation oncology, our field seems like it’s changing every year with advancements in technology,” he said. “Even in the past decade, radiation delivery has improved for patients, and this is nationwide, worldwide.”

Talking with CURE as part of the “Speaking Out” video series, Solhjem discussed advancements in treating patients with prostate cancer, with methods of delivering greater doses of radiation in fewer treatments via tactics such as stereotactic body radiation therapy (SBRT) and high dose rate (HDR) brachytherapy.

He also discussed study findings published in JAMA Oncology that showed that among patients with prostate cancer, MRI-guided radiation therapy resulted in a 24.4% incidence of grade 3 (severe) or higher genitourinary toxic effects versus a 43.4% incidence among patients treated with computerized tomography (CT)-guided treatment. Likewise, acute grade 2 (moderate) or higher gastrointestinal toxic effects occurred in none of the patients treated with MRI-guided radiation therapy and 10.5% of the patients who received treatment with CT-guided therapy.

“Compared with CT guidance, MRI-guided SBRT significantly reduced both moderate acute physician-scored toxic effects and decrements in patient-reported quality of life,” researchers wrote in the study findings, noting that “longer-term follow-up will confirm whether these notable benefits persist.”

Q: What are some recent advancements in the field of radiation oncology that patients with prostate cancer should be aware of?

A: We want to obviously cure prostate cancer, and prostate cancer is very curable with radiation. … There are organs surrounding the prostate gland that need to be carefully spared from radiation. One is the rectal wall, which is just behind the prostate gland, and then the bladder wall, which is just above the prostate gland. So one fairly recent advancement is using a rectal spacer, which actually is a gel-like material that’s placed between the prostate gland and the rectum before radiation even starts, and it acts to push the rectum away and thereby spare the rectal wall from radiation dose. So that’s a huge advancement. And recently, we’re starting to do that very frequently.

Another advancement that is at least very important with SBRT is the use of MRI-guided treatment. In terms of imaging the prostate gland, there’s MRI, there’s CT, there’s PET [positron emission tomography] scan and ultrasound. And by far the best in terms of image quality and anatomical detail is MRI.

Fortunately, Providence Cancer Institute purchased an MRI-guided treatment machine for our department so we can deliver this amazing treatment.

Basically, patients come in every day [and] an MRI scan is taken. And we plan or replan the treatment every day to the unique anatomy on that day. The rectal wall is very visible, the bladder wall, the urethra. I think with the extreme accuracy of the MRI scan, we can deliver treatments much more accurately and spare the organs around the prostate gland better.

Q: What advantages does MRI-guided radiation therapy offer versus more traditional forms of radiation therapy in prostate cancer?

A: I think it is just that: the very detailed anatomy. When we plan or replan the treatment every time … how full the bladder is or how empty the bladder is can make a difference. Same with rectal contents. It’s a very customized treatment delivery for each treatment, so it takes a fair amount of time; patients are in the unit for an hour to an hour and a half or so. But I think in the long run, the reduction in the radiation dose to the rectum and the bladder will lead to fewer complications and risks. And, coupling the MRI-guided treatment with the rectal spacer should even limit that further for patients.

We’re also starting to use the spacer for the high dose rate [brachytherapy]. So HDR brachytherapy is basically using needles as conduits for a radioactive source. So it’s started under general anesthesia. We’re going to be placing the rectal spacer to move the rectum away from the prostate, then place the needles into the prostate. And then once they’re in place, the radioactive source can go into each needle and deliver the radiation dose.

Q: What patients are ideal candidates for this line of treatment?

A: We separate or classify patients into low, intermediate and high risk. And during the time of consultation, we make a determination whether [there are] lymph node risks; the prostate cancer can first spread to lymph nodes in the pelvis. And if we make that determination that there might be a chance of having lymph nodes involved, we typically use [intensity-modulated radiation treatment] for treating the lymph nodes in the prostate gland, and that’s a longer course of treatment. And we typically do 28 treatments or five and a half weeks for those patients. But if there is minimal lymph node risk and we’re just treating the prostate gland and the seminal vesicles, they are then candidates for the MRI-guided SBRT or the HDR brachytherapy.

Q: What does recent research have to say about MRI-guided radiation therapy?

A: There are two ways of doing the SBRT. The MRI-guided treatment is what we do here. And it’s really compared with CT-based delivery of SBRT. … One study did compare the two. [For] MRI-guided delivery versus CT-guided delivery, at least in the short term, the bladder and rectal side effects were actually quite a bit less with the MRI-guided [treatment], and I think that just has to do with the better visualization of the prostate gland and its interface or proximity to the rectum and the bladder and the ability to spare those organs. We really don’t know the long-term potential benefits, but I’m guessing there will be benefits to MRI-guided SBRT in the long term as well.

Transcript edited for clarity and conciseness.

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