Hollings radiation oncologist tests methods to reduce side effects in prostate cancer treatment

Radiation oncologists treating prostate cancer patients must find the right balance between using enough radiation to kill the cancer so that it won’t come back and limiting the amount of radiation that nearby healthy tissues absorb.

But when it comes to a newer method of delivering radiation therapy, called stereotactic ablative body radiotherapy (SABR) (also known as SBRT – stereotactic body radiation therapy), there’s not yet an agreed-upon standard.

“For this technique, even though it's being done around the country, we don't truly know the optimal radiation dose. There's a range of doses that physicians use,” said Harriet Eldredge-Hindy, M.D., a radiation oncologist at MUSC Hollings Cancer Center who treats people with prostate and other genitourinary cancers as well as breast and gynecologic cancers.

To provide some answers, Eldredge-Hindy developed and launched a clinical trial that combines SABR at the higher end of safe doses with physical measures to protect healthy tissues and strict targeting of the cancer.

"What is novel about this trial is that we are planning and delivering the radiation in a new way so that we can minimize the dose to healthy tissues. We're trying to improve upon standard practice by giving lower doses of radiation to those healthy tissues: the urethra, the pudendal arteries and the rectum.”

Harriet Eldredge-Hindy, M.D.

The trial is for men with low-risk or intermediate-risk cancer that hasn’t spread beyond the prostate.

Inserting a gel spacer between the prostate and rectum creates just enough physical space between healthy tissues and the cancerous target to protect the healthy tissue more fully. Placing a foley catheter in the bladder enables the urethra to be visible during radiation planning so that the radiation dose to the urethra can be reduced. A rectal balloon helps to hold the prostate still.

“Your internal organs are moving all the time,” Eldredge-Hindy explained. They move by millimeters as one breathes in and out, for example. “Also, as the bladder and the rectum fill and empty, the prostate can kind of bob around a little bit.”

With the prostate moving ever so slightly, the doctor must aim the radiation toward a larger area to ensure it hits the tumor. But if the prostate is held still, the target area can be tightened up.

“With the doses that we're giving, people have used those doses before, but not with these organ-sparing techniques,” Eldredge-Hindy said. “What is novel about this trial is that we are planning and delivering the radiation in a new way so that we can minimize the dose to healthy tissues. We're trying to improve upon standard practice by giving lower doses of radiation to those healthy tissues: the urethra, the pudendal arteries and the rectum.”

Lowering the dose to those areas should reduce side effects. Eldredge-Hindy's team will be following up with study participants to get their reports of side effects and compare them to patient reports from large national trials of SABR without the organ-sparing techniques.

Cancer clinical trials: creating knowledge

Clinical trials are integral to the work at Hollings. As a National Cancer Institute-designated cancer center – the only one in South Carolina – Hollings not only treats patients with the latest methods but also conducts research to develop new treatments and techniques and add to scientific knowledge.

Participating in a cancer clinical trial means different things to different patients. For some, there’s pride in helping future cancer patients. For others, there’s hope that the treatment being tested will be better than the standard of care.

And the standard of care changes over time as new studies confirm – or disprove – the effectiveness of a treatment. For example, study results released at the American Society for Radiation Oncology annual meeting in October indicate that SABR could be on its way to becoming a new standard of care. SABR involves using a higher dose of focused radiation but fewer treatment sessions.

“Whether or not the treatment is successful is going to be determined by what the patients tell us their symptoms are.”

Harriet Eldredge-Hindy, M.D.

At Hollings, the standard course of radiation therapy for low- and intermediate-risk prostate cancer would be 20 treatment sessions. The sessions are daily, Monday through Friday.

Men enrolled in this trial using SABR, however, are treated in five sessions, performed every other day.

The goal is to enroll 36 men in the trial; already seven patients have opted for this treatment.

Eldredge-Hindy noted that other recent clinical trials have shown good results in terms of getting rid of the cancer. This trial is focused on getting good clinical results while also reducing toxicity, or side effects.

“Whether or not the treatment is successful is going to be determined by what the patients tell us their symptoms are,” she said.

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