A widely-available yet expensive radiotherapy technique used to treat prostate cancer patients after surgery has promising benefits -- higher dose and less damage to the rectum and bladder -- compared to a less precise technique, Thomas Jefferson University researchers document for the first time in a new study published in Practical Radiation Oncology.
A team of radiation oncologists and medical physicists, including lead author Amy Harrison, M.S., the medical physics clinical supervisor at Jefferson, show that intensity-modulated radiotherapy (IMRT) allows a higher dose to be delivered to the area after their glands have been removed while maintaining the same dose to the rectum and bladder compared to 3D conformal radiation therapy.
Higher doses to the prostate bed have been shown to be more effective in that setting for controlling prostate-specific antigen (PSA) levels.
IMRT is currently being used at some centers in the United States, including the Kimmel Cancer Center, to treat men after they've had their prostate glands removed, but detailed data are limited evaluating the advantages of this approach compared to 3D conformal radiation therapy. In other words, documented justification for the approach was lacking.
"This is the first contemporary study to look at IMRT versus 3D radiation therapy for post-op patients using consensus guidelines," said Timothy Showalter, M.D., assistant professor of Radiation Oncology at Thomas Jefferson University, and an expert in image-guided therapy of prostate cancer. "This is also filling a gap for information that no one supplied before to show that this radiotherapy is beneficial in the postoperative setting, similar to its role in non-surgical approaches."
"The reason that it's more and more relevant now is that there are emerging data to support doing adjuvant radiation therapy after prostatectomy for high risk patients," he added.
There a variety of toxicities associated with radiation therapy after a prostatectomy, including late gastrointestinal bleeds, loose stools and painful bowel moments, but IMRT can minimize damage that can lead to such side effects.
"The biggest benefit for our patients who have a PSA failure after radical prostatectomy is to be able to deliver high dose radiation while sparing normal tissue," said Dr. Showalter.
Future studies, the researchers report, should determine whether these advantages translate into improved clinical outcomes for prostate cancer patients.
- Amy Harrison, Matthew Studenski, Arthur Harvey, Edouard J. Trabulsi, Ying Xiao, Yan Yu, Adam P. Dicker, Timothy N. Showalter. Potential for dose escalation in the postprostatectomy setting with intensity-modulated radiation therapy: a dosimetric study using EORTC consensus guidelines for target volume contours. Practical Radiation Oncology, 2011; 1 (2): 105 DOI: 10.1016/j.prro.2010.10.005
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