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Prostate Cancer: Assessments of Intensity-Modulated Radiation Therapy from Two Brachytherapists

Hyer, Richard

doi: 10.1097/01.COT.0000294685.87089.db

CHICAGO—Intensity-modulated radiation therapy (IMRT) is a clean, quick, noninvasive, and accurate way to treat prostate cancer. It can spare sensitive bladder and small bowel tissue, and the pubic arch interference that is such an issue with brachytherapy presents no problem for radiation.

So said Juanita Crook, MD, Professor of Radiation Oncology at the University of Toronto and Head of the Prostate Brachytherapy Program at Princess Margaret Hospital, speaking here at the 10th Annual Windy City “Shoot-Out” about controversies about early-stage prostate cancer.

The other speaker in the session, though, Steven Kurtzman, MD, Director of Brachytherapy at Western Radiation Oncology in San Mateo, CA, was less enthusiastic.

“I feel there is no better conformal radiation treatment than good brachytherapy,” he said. He granted, though, that IMRT could be non-invasive, result in less short-term urinary morbidity, and was a “one size fits all” treatment.

IMRT uses non-uniform beam intensities to tailor a dose to the irregular volume of the cancer or irregular target. This has obvious advantages in prostate cancer, where disease distribution is not uniform.



“I'm sure my colleague is going to tell you that brachytherapy is the best way of getting a high dose into the prostate, but with dose escalation, you can achieve with IMRT a very definitive benefit in terms of biochemical relapse and survival.” Dose is also an independent predictor of biochemical relapse-free survival.

Technical improvements to this modality have decreased the rectal toxicity that used to be a problem,” Dr. Crook said. “With IMRT you get rectal-wall sparing right up through the high-dose range, and that's what makes it safe at these doses.”

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Consequences of Brachytherapy

Brachytherapy is not without consequences, including high rates of urinary retention, she said. “You don't see anywhere near this urinary toxicity with IMRT.”

The state of the art in brachytherapy, Dr. Kurtzman said, is transperineal and ultrasound-guided, using intraoperative computer-based dosimetry. The treatment is capable of curing prostate cancer while reducing the morbidity long associated with all definitive prostate cancer treatments.

“Brachytherapy allows for highly conformal dose delivery,” he said. “It is convenient and tolerable, and data show excellent outcomes.”

He allowed that it is an invasive procedure requiring anesthesia and often results in increased short-term urinary morbidity. Brachytherapy also requires a skilled operator, “but, in many ways it is easier to master than IMRT,” he said.

A patient receiving IMRT could conceivably require daily weekday treatment for eight or more weeks, Dr. Kurtzman said, whereas brachytherapy is done in one sitting. “It is not an ongoing process with a lot of opportunities for error.”

The future of brachytherapy may involve new isotopes such as Cesium-131, he added. Cs131 has a 9.7-day half-life with a desired dose of 100 Gy. Dr. Kurtzman said that it is not yet clear whether this will change the side-effect profile.

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Dr. Crook's Rebuttal

“I enjoyed your talk, and I've used many of your arguments myself many times,” Dr. Crook said after Dr. Kurtzman's presentation. “I do agree that there's no better conformal therapy than well-performed brachytherapy.”

In a later interview, Dr. Crook noted that brachytherapy represented the majority of her practice and that IMRT requires a team approach and is expensive; the greatest strength, she said, is its ability to shape isodose curves.

It was not known whether brachytherapy is sufficient for intermediate-risk disease or whether it should be combined with external-beam, she said. She recommended dose-escalated IMRT of 78 to 80 Gy and said that IMRT is the treatment of choice for high-risk prostate cancer.

© 2005 Lippincott Williams & Wilkins, Inc.
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