A 2-year collaboration between gastroenterologists and radiation oncologists at University of Miami Health System (UM) has resulted in a new application of endoscopic ultrasound (EUS) that benefits prostate cancer patients.

Afonso Ribeiro, MD, 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 Gastrointestinal Endoscopy.

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. The work by Ribeiro and his team suggests 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 proved 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.