Prostate tumor alignment and continuous, real-time adaptive radiation therapy using electromagnetic fiducials: clinical and cost-utility analyses.

OBJECTIVE: To evaluate the accuracy, utility, and cost effectiveness of a new electromagnetic patient positioning and continuous, real-time monitoring system, which uses permanently implanted resonant transponders in the target (Calypso 4D Localization System and Beacon transponders, Seattle, WA) to continuously monitor tumor location and movement during external beam radiation therapy of the prostate. MATERIALS AND METHODS: This clinical trial studied 43 patients at 5 sites. All patients were implanted with 3 transponders each. In 41 patients, the system was used for initial alignment at each therapy session. Thirty-five patients had continuous monitoring during their radiation treatment. Over 1,000 alignment comparisons were made to a commercially available kV X-ray positioning system (BrainLAB ExacTrac, Munich, Germany). Using decision analysis and Markov processes, the outcomes of patients were simulated over a 5-year period and measured in terms of costs from a payer's perspective and quality-adjusted life years (QALYs). RESULTS: All patients had satisfactory transponder implantations for monitoring purposes. In over 75% of the treatment sessions, the correction to conventional positioning (laser and tattoos) directed by an electromagnetic patient positioning and monitoring system was greater than 5 mm. Ninety-seven percent (34/35) of the patients who underwent continuous monitoring had target motion that exceeded preset limits at some point during the course of their radiation therapy. Exceeding preset thresholds resulted in user intervention at least once during the therapy in 80% of the patients (28/35). Compared with localization using ultrasound, electronic portal imaging devices (EPID), or computed tomography (CT), localization with the electromagnetic patient positioning and monitoring system yielded superior gains in QALYs at comparable costs. CONCLUSIONS: Most patients positioned with conventional tattoos and lasers for prostate radiation therapy were found by use of the electromagnetic patient positioning and monitoring system to have alignment errors exceeding 5 mm. Almost all patients undergoing external beam radiation of the prostate have been shown to have target organ movement exceeding 3 mm during radiation therapy delivery. The ability of the electromagnetic technology to monitor tumor target location during the same time as radiation therapy is being delivered allows clinicians to provide real time adaptive radiation therapy for prostate cancer. This permits clinicians to intervene when the prostate moves outside the radiation isocenter, which should decrease adverse events and improve patient outcomes. Additionally, a cost-utility analysis has demonstrated that the electromagnetic patient positioning and monitoring system offers patient outcome benefits at a cost that falls well within the payer's customary willingness to pay (WTP) threshold of $50,000 per QALY.

Accuracy of a wireless localization system for radiotherapy.

PURPOSE: A system has been developed for patient positioning based on real-time localization of implanted electromagnetic transponders (beacons). This study demonstrated the accuracy of the system before clinical trials. METHODS AND MATERIALS: We describe the overall system. The localization component consists of beacons and a source array. A rigid phantom was constructed to place the beacons at known offsets from a localization array. Tests were performed at distances of 80 and 270 mm from the array and at positions in the array plane of up to 8 cm offset. Tests were performed in air and saline to assess the effect of tissue conductivity and with multiple transponders to evaluate crosstalk. Tracking was tested using a dynamic phantom creating a circular path at varying speeds. RESULTS: Submillimeter accuracy was maintained throughout all experiments. Precision was greater proximal to the source plane (sigmax = 0.006 mm, sigmay = 0.01 mm, sigmaz = 0.006 mm), but continued to be submillimeter at the end of the designed tracking range at 270 mm from the array (sigmax = 0.27 mm, sigmay = 0.36 mm, sigmaz = 0.48 mm). The introduction of saline and the use of multiple beacons did not affect accuracy. Submillimeter accuracy was maintained using the dynamic phantom at speeds of up to 3 cm/s. CONCLUSION: This system has demonstrated the accuracy needed for localization and monitoring of position during treatment.

An Internet-ready database for prospective randomized clinical trials of high-dose-rate brachytherapy for adenocarcinoma of the prostate.

PURPOSE: To demonstrate a new interactive Internet-ready database for prospective clinical trials in high-dose-rate (HDR) brachytherapy for prostate cancer. METHODS AND MATERIALS: An Internet-ready database was created that allows common data acquisition and statistical analysis. Patient anonymity and confidentiality are preserved. These data forms include all common elements found from a survey of the databases. The forms allow the user to view patient data in a view-only or edit mode. Eight linked forms document patient data before and after receiving HDR therapy. The pretreatment forms are divided into four categories: staging, comorbid diseases, external beam radiotherapy data, and signs and symptoms. The posttreatment forms separate data by HDR implant information, HDR medications, posttreatment signs and symptoms, and follow-up data. The forms were tested for clinical usefulness. CONCLUSION: This Internet-based database enables the user to record and later analyze all relevant medical data and may become a reliable instrument for the follow-up of patients and evaluation of treatment results.

Adjuvant high dose rate vaginal brachytherapy as treatment of stage I and II endometrial carcinoma.

OBJECTIVE: To evaluate the efficacy of high dose rate vaginal brachytherapy in the treatment of International Federation of Gynecology and Obstetrics stage IB, IC, and II endometrial carcinoma after surgical staging and complete lymphadenectomy. METHODS: All patients with stage IB, IC, or II adenocarcinoma or adenosquamous carcinoma of the endometrium who received postoperative high dose rate vaginal brachytherapy at our institution between June 1, 1989, and June 1, 1999, were eligible. High dose rate vaginal brachytherapy was delivered in three fractions of 700 cGy. Retrospective chart review was performed. Kaplan-Meier estimates were calculated for disease-free and overall survival. RESULTS: One hundred sixty-four women were identified. Fifty-six percent had stage IB disease, 30% had stage IC disease, and 14% had stage II disease. Approximately one third of patients had high-grade lesions and nearly 40% had deep myometrial invasion. Median follow-up was 65 months (range 6-142 months). To date, 14 patients have had recurrence; 2 at the vaginal apex, 9 at distant sites, 1 at the pelvic sidewall, 1 simultaneously in the pelvis and at a distant site, and 1 at an unknown site. Both patients with vaginal apex recurrences had salvage therapy and are now free of disease. The overall 5-year survival and disease-free survival rates were 87% and 90%, respectively. There were no Radiation Therapy Oncology Group grade 3 or 4 toxicities. High dose rate vaginal brachytherapy was approximately $1,000 less expensive than external-beam whole-pelvic radiation. CONCLUSIONS: Adjuvant high dose rate vaginal brachytherapy in thoroughly staged patients with intermediate-risk endometrial carcinoma provides excellent overall and disease-free survival with less toxicity and at less cost compared with whole-pelvic radiation.