UM Physician Uses Endoscopic Ultrasound to Provide Targeted Radiation Therapy
Use in Prostate Cancer Shows Promise for Other Applications
A two-year collaboration between gastroenterologists and radiation oncologists at UHealth — University of Miami Health System has resulted in a new application of endoscopic ultrasound (EUS) that benefits prostate cancer patients. Afonso Ribeiro, M.D., associate professor of medicine in the Division of Gastroenterology, led the study which examined the feasibility and safety of using EUS to implant markers in prostate cancer patients needing targeted radiation therapy. The results have been published in the September issue of the journal Gastrointestinal Endoscopy.
Endoscopic ultrasound (EUS) is a technique that provides detailed ultrasound imaging of organs adjacent to the gastrointestinal tract. Physicians at UM’s Sylvester Comprehensive Cancer Center use it to diagnose and stage several gastrointestinal malignancies such as pancreatic, esophageal and rectal cancers. Ribeiro, Julie Yang, M.D., gastroenterology fellow, and May Abdel-Wahab, M.D., associate professor of radiation oncology at Sylvester, have now shown how EUS can be used to offer more targeted radiation therapy to prostate cancer patients.
In cases of localized prostate cancer, external beam radiation is a standard therapy often used successfully in a dose-dependent fashion. However, increasing the dose can lead to an increase in toxicity to healthy tissue if close attention is not paid to the delivery system and localization techniques. The prostate has proven to be a challenging target because its position changes depending on the dynamics of its neighboring bladder and rectum.
Intensity-modulated radiotherapy (IMRT) provides a precise dose of radiation which can be intensified around a defined target. Physicians, however, must define or localize that moving target on the diseased prostate. Transabdominal ultrasound has been used to target the tumor, but that method can be time consuming and can vary according to the operator’s proficiency.
Implanting radiopaque markers or fiducials, which serve as reference points to delineate organs, has provided a far more accurate target for IMRT. In the past, urologists and radiation oncologists have placed these tumor “markers” in prostate and pancreatic cancer patients using either transrectal or transperineal ultrasound guidance.
In this study, Ribeiro and his team successfully used EUS to place two to three fiducial markers into each of 16 prostate patients who were under intravenous sedation, providing radiation oncologists with an exact target for IMRT or Cyberknife therapies. The success of the implants indicates that gastroenterologists can play an important role by providing an alternative method for implanting fiducials through EUS.
Maria T. Abreu, M.D., professor of medicine and chief of the Division of Gastroenterology, says this is the “first description of using state-of-the-art endoscopic equipment to place these fiducials in a targeting position in the prostate. It’s also much more comfortable for the patient.”
Not only do the fiducials present a more accurate target for dose escalated radiation therapy, they also give physicians a frame of reference, making it possible to “track” the site for any local recurrence. Ribeiro points out that “this collaborative work highlights the importance of multidisciplinary cancer care that is only possible at a comprehensive cancer center.”
Future studies will take a closer look at the clinical outcome when using this technique for fiducial placement. Researchers will also examine the cost effectiveness of using EUS when compared to alternative methods.