MRI-Based Treatment May Decrease Prostate Cancer Side Effects

Stereotactic body radiotherapy guided by magnetic resonance imaging (MRI) significantly reduced moderate side effects and improved quality of life for patients with prostate cancer compared with radiotherapy guided by standard of care, according to recent study results.

The study, which was published in JAMA Oncology, included 156 patients who received stereotactic body radiotherapy guided by computed tomography (CT), the standard of care, (77 patients) or MRI (79 patients).

The occurrence of moderate or worse genitourinary and gastrointestinal side effects were significantly lower with MRI-guided therapy, compared with CT-guided. Additionally, MRI-guidance was associated with a smaller percentage of patients with a 15 point or greater increase in their International Prostate Symptom Score — which measures prostate cancer-related symptoms — at one month.

MRI-guided therapy also significantly reduced the percentage of patients with clinically significant decrease in Expanded Prostate Cancer Index Composite-26 (which measures health-related quality of life) bowel scores, at one month.

This means that both physician-evaluated, and patient-reported symptoms were decreased when stereotactic body radiotherapy was guided by MRI, compared with CT.

“In summary, what we have seen in this randomized trial is that using this MRI-guided machine to really drastically narrow the margins around the prostate substantially reduced urinary and bowel side effects, both as scored by the doctor treating the patients and scored by the patients themselves,” Dr. Amar U. Kishan, lead author on the study and associate professor of radiation oncology and urology at the University of California, Los Angeles, said in an interview with CURE®.

Kishan explained that when treating prostate cancer with radiation, one of the main considerations for clinicians is precisely target the prostate; however, it is a moving target, even during treatment, which can often lead to side effects in other areas of the body such as the bladder or rectum. Previously, using a CT-guided approach they would have to place medal markers in the prostate to specifically target it during radiation.

But with the MRI-based approach, they are able to target the prostate directly without any markers needed and as seen in these data, it may result in less side effects for patients because of its precision.

“Some of the dark targeting and drawing out of the prostate may be a little bit smoother and less error prone because ultimately we are using an MRI … when we're planning and developing our radiation plan,” he said.

Treatment options for localized prostate cancer often have excellent outcomes, Kishan highlighted, so it is important that they don’t have to experience side effects and have the option of an MRI-guided treatment.

“Whether you do surgery or radiation or any of the different forms of radiation, the outcomes are generally excellent with prostate cancer, which is very, very good. But in some ways that even makes it that more important that the side effects are low because these men are going to live rid of their cancer, and they're going to live with potentially the side effects of their treatment,” he noted. “So in that type of scenario, it's even more important that the side effect profile is minimized. And so, because the bar is already so high for cure, now when we're dealing with localized prostate cancer, most of the research effort is actually dedicated towards reducing side effects.”

Furthermore, patients with prostate cancer can use this data to their advantage and may want to consider an MRI-based approach when thinking about treatment options.

“If you have localized prostate cancer and you're thinking about your treatment options, I think it's important to talk to both the urologist and the radiation oncologists to understand what your treatment options are and you can inquire about some of these newer technologies like MRI guided radiation,” Kishan concluded.

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