Clinical Research Highlights - A Multi-Institutional Study and Report of a Clinical Experience

Study overview A recent clinical study was conducted using the Calypso® 4D Localization System™ and Beacon® electromagnetic transponders. This study is the only continuous, real-time, and objective setup and tracking study of the prostate during external beam radiation therapy, now, with over 2000 fractions recorded.

Purpose To report the clinical experience with an electromagnetic treatment target positioning and continuous monitoring system in patients with localized prostate cancer receiving external beam radiation therapy.

Methods/Materials The Calypso System and implanted Beacon® transponders were used at five centers to position 41 patients over a full course of therapy. Electromagnetic positioning was compared to setup using skin marks and to stereoscopic X-ray localization of the Beacon® transponders. Continuous monitoring was performed in 35 patients.

Results of the study

 

Usability

• Setup alignment - range 35s to 108s
• Calypso System localization and tracking was completed within standard appointment period
• Retraining was not necessary for RT(T)s trained other RT(T)s

 

Accuracy

• Excellent agreement between Calypso System and kV x-ray
• Alignment relative to laser/skin mark setup (1524 fractions)
• >75% of patients had >5mm misalignment at setup

 

Tracking (n=1157 fractions)

• Motion exceeded tracking limits ~ 30% of fractions
• Tracking limits exceeded in 97% (34/35) of patients
• Types of motion were stable targets, drifting excursions, erratic excursions, self-resolving excursions, and non-resolving excursions

 

Beacon® electromagnetic transponder positional stability

• Beacon® transponders typically stable by 4 days post-implant (all by 14 days) and <1mm standard deviation for inter-transponder distances over time

 

Reliability

• 100% of Beacon® transponders remained functional throughout therapy
• The Calypso System performance was exceptional with 99.4% system uptime

Study conclusion
The Calypso System is a clinically efficient and objective localization method for positioning prostate patients undergoing radiation therapy. Initial treatment setup can be performed rapidly, accurately, and objectively before radiation delivery. The extent and frequency of prostate motion during radiation therapy can be easily monitored and used for motion management.