The university of California, San Francisco (UCSF) experience with permanently implanted gold markers for daily prostate realignment during radiation therapy

Abstract

Purpose/Objective: Work at our institution and others have shown that set up errors are common and can be as large as 1.5cm. Our objective was to improve prostate localization and the accuracy of patient repositioning during daily radiation therapy for prostate cancer. We now report our experience with this new technique and the role Urologists can play in the routine management of patients receiving radiation therapy. Materials/Methods: Transrectal ultrasound (TRUS) guidance in an office setting has been used in the placement of three 24kt. gold radio-opaque markers by a single urologist at our institution (K.S.). Each gold marker is 3mm in length × 1.6mm in diameter. The gold markers are biologically inert and are made by a local jeweler. Before placement of the radio-opaque markers local anesthesia is injected into the prostate to minimize patient discomfort during the procedure. A 14 gauge Tru-cut needle is used to deploy the radio-opaque markers. Two seeds are routinely placed into the base of the prostate bilaterally and a single marker is placed into the prostatic apex in the midline. The procedure takes approximately 10 minutes to perform. An amorphous silicon flat panel electronic portal imaging device (EPID) is used to generate online electronic portal imaging to locate the gold markers prior to each treatment. Typically images were acquired using 2MU (monitored units) and 18MV photons. The expected marker location was extracted from a digital reconstructed radiograph (DRR). Results: Radio-opaque gold markers were placed prior to external beam radiotherapy (EBRT) in 112 patients over the past 61 months. Initially we placed radio-opaque markers for local disease recurrence requiring salvage radiotherapy. We are now also placing gold markers for primary radiotherapy and for special instances such as EBRT in the morbidly obese patient. In our last 10 patients we have been able to use smaller radio-opaque markers 3mm × 1.1mm and to deploy the gold markers using a 17gauge Tru-cut needle. This has allowed us to perform the procedure without the administration of local anesthesia and the gold markers are clearly visualized using the amorphous silicon flat panel. To date no complications attributed to gold marker placement has been reported. The gold radio-opaque markers are clearly seen on electronic portal imaging. Localization of gold markers has decreased the time required for the daily delivery of EBRT. Treatment set up error has been limited to < 3mm. Conclusions: Radio-opaque gold marker placement prior to external beam radiotherapy is safe and has the potential to improve localization and targeting accuracy. We have now routinely incorporated this technique into our standard practice and believe this innovative technique should become the new standard in patients receiving external beam radiotherapy. View Large Image Figure ViewerDownload (PPT)