Promising Results Reported for System Monitoring Organ Motion During RadiotherapyAt the 2006 meeting of the American Society for Therapeutic Radiology and Oncology (ASTRO) in November there were 10 abstracts presented that describe a new system for measuring and monitoring organ motion in real time during external beam radiotherapy (EBRT). The Calypso® 4D Localization System should enable radiation oncologists to deliver more accurate radiation to various cancers by making changes during the delivery of EBRT.

Several techniques have been used to more accurately deliver EBRT to cancers while sparing normal tissue, including conformal radiotherapy and intensity modulated radiation therapy (IMRT). These techniques offer advantages over conventional methods of EBRT delivery but do not account for significant organ motion during the delivery of radiation therapy. The newly developed Calypso system utilizes proprietary electromagnetic technology in conjunction with implanted Beacon® electromagnetic transponders. The electromagnetic array continuously locates the transponders and transfers this information to the linear accelerator during EBRT. This technique was given FDA 510 (k) clearance in 2006.

Researchers at the ASTRO meeting reported two preclinical studies in dogs using the Calypso® 4D Localization System. Researchers from Washington University presented data on the successful bronchoscopic implantation of transponders and gold fiducials in the canine lung.[[1]](http://news.cancerconnect.com/promising-results-reported-for-system-monitoring-organ-motion-during-radiotherapy/#_edn1 "_ednref1") These same researchers also demonstrated that the Calypso system provided continuous measurements of lung tissue movement during breathing without the use of ionizing radiation.[[2]](http://news.cancerconnect.com/promising-results-reported-for-system-monitoring-organ-motion-during-radiotherapy/#_edn2 "_ednref2")

A study from five radiation centers involving 29 radiation therapists reported on various aspects of the Calypso system compared to standard tumor localization methods using ionizing radiation for set up prior to EBRT. One study evaluated the implantation of the electromagnetic transponders into 43 patients with prostate cancer.[[3]](http://news.cancerconnect.com/promising-results-reported-for-system-monitoring-organ-motion-during-radiotherapy/#_edn3 "_ednref3") They reported that the average placement time for three transponders under ultrasound control was less than 10 minutes. They reported that all transponders functioned fully during a full treatment course of EBRT in all patients. They also reported that transponders retain stable geometry over time in patients with prostate cancer receiving neoadjuvant and/or concurrent androgen suppression therapy.[[4]](http://news.cancerconnect.com/promising-results-reported-for-system-monitoring-organ-motion-during-radiotherapy/#_edn4 "_ednref4")

These researchers also reported that this was an efficient system for aligning the prostate for EBRT in 41 patients with prostate cancer using three transponders.[[5]](http://news.cancerconnect.com/promising-results-reported-for-system-monitoring-organ-motion-during-radiotherapy/#_edn5 "_ednref5") They suggested that this non-ionizing system had the advantage of allowing the therapist to remain in the room during setup and verification in contrast to conventional systems, which require conventional X-ray exams. The authors also reported that the total alignment time with the Calypso system was less than 2 minutes.

These same researchers reported on variations in prostate rotation using the Calypso system.[[6]](http://news.cancerconnect.com/promising-results-reported-for-system-monitoring-organ-motion-during-radiotherapy/#_edn6 "_ednref6") They stated that intrafractional prostate motion can exceed 3-5 mm and the real time system allows for intervention to correct for such motion.[[7]](http://news.cancerconnect.com/promising-results-reported-for-system-monitoring-organ-motion-during-radiotherapy/#_edn7 "_ednref7")

This same group of patients with prostate cancer also had localization studies performed with radio-opaque transponders using the Exac Trac X ray system.[[8]](http://news.cancerconnect.com/promising-results-reported-for-system-monitoring-organ-motion-during-radiotherapy/#_edn8 "_ednref8") This method was compared to the Calypso method, and the two techniques performed equally well. However, one advantage to the Calypso system is that it can be performed without ionizing radiation.

Real-time motion in the prostate gland was measured in this same group of men with prostate cancer.[[9]](http://news.cancerconnect.com/promising-results-reported-for-system-monitoring-organ-motion-during-radiotherapy/#_edn9 "_ednref9")They concluded that the extent and frequency of real time motion in the prostate during radiotherapy was significant and could affect the outcome of therapy. They suggest that changes during the delivery of EBRT can now be made.

The final abstract at ASTRO evaluated interventions to correct for target motion detected by the Calypso system.[[10]](http://news.cancerconnect.com/promising-results-reported-for-system-monitoring-organ-motion-during-radiotherapy/#_edn10 "_ednref10") They reported that target motion exceeding the tracking limits of 3 or 5 mm in 34 of 35 patients. This occurred during 31% of all radiation fractions. The following interventions were carried out during treatment:

  • Radiation delivery was stopped during 0.4% of fractions with a maximum of 7% in one patient.
  • Radiation delivery was delayed in 2.7% of fractions with a maximum of 18% in one patient.
  • The patient was realigned in 8.2% of all fractions for a maximum of 50% in one patient.

These authors stated that the Calypso® 4D Localization System allows for therapeutic interventions during actual delivery of radiotherapy, which is unique to this system.

Comments: These studies suggest that the Calypso system could improve the results of radiotherapy in patients with cancer where motion is a problem such as prostate and lung.

References

[[1]](http://news.cancerconnect.com/promising-results-reported-for-system-monitoring-organ-motion-during-radiotherapy/#_ednref1 "_edn1") Parikh PJ, Mayse ML, Chaudhari A, et al. A comparison of animal health impacts and implant stability between bronchoscopic implanted gold fiducials and electromagnetic transponders in canine lung tissue. Proceedings of the 48th annual meeting of the American Society for Therapeutic Radiology and Oncology. November 2006; Abstract 2495, Published in the International Journal of Radiation Oncology* Biology*Physics.

[[2]](http://news.cancerconnect.com/promising-results-reported-for-system-monitoring-organ-motion-during-radiotherapy/#_ednref2 "_edn2") Lechleiter KM, Low DA, Chaudhari A, et al. Characterization of external breathing surrogate using implanted electromagnetic transponders in canine lungs. Proceedings of the 48th annual meeting of the American Society for Therapeutic Radiology and Oncology. November 2006; Abstract 97, Published in theInternational Journal of Radiation Oncology* Biology*Physics.

[[3]](http://news.cancerconnect.com/promising-results-reported-for-system-monitoring-organ-motion-during-radiotherapy/#_ednref3 "_edn3") Mahadevan A, Klein E, Djemil T, et al. Tolerance, stability and reliability of implanted electromagnetic transponders in the prostate: A multi-center analysis. Proceedings of the 48th annual meeting of the American Society for Therapeutic Radiology and Oncology. November 2006; Abstract 2213, Published in the International Journal of radiation Oncology* Biology*Physics.

[[4]](http://news.cancerconnect.com/promising-results-reported-for-system-monitoring-organ-motion-during-radiotherapy/#_ednref4 "_edn4") Weinstein G, Jani S, Kupelian P, et al. Stability of intraprostatic electromagnetic transponders in patients receiving radiation therapy, with and without neoadjuvant and /or concurrent androgen suppression therapy. Proceedings of the 48th annual meeting of the American Society for Therapeutic Radiology and Oncology. November 2006; Abstract 2266, Published in the International Journal of radiation Oncology* Biology*Physics.

[[5]](http://news.cancerconnect.com/promising-results-reported-for-system-monitoring-organ-motion-during-radiotherapy/#_ednref5 "_edn5") Beyer D, Liu D, Flores I, et al. Efficiency of a non-ionizing target localization system for radiation therapy. Proceedings of the 48th annual meeting of the American Society for Therapeutic Radiology and Oncology. November 2006; Abstract 2290, Published in the International Journal of Radiation Oncology* Biology*Physics.

[[6]](http://news.cancerconnect.com/promising-results-reported-for-system-monitoring-organ-motion-during-radiotherapy/#_ednref6 "_edn6") Djemil T, Mahadevan A, Kupelian P, et al. Prostate rotation measured by electromagnetic tracking system: A multi-center analysis. Proceedings of the 48th annual meeting of the American Society for Therapeutic Radiology and Oncology. November 2006; Abstract 2236, Published in the International Journal of Radiation Oncology* Biology*Physics.

[[7]](http://news.cancerconnect.com/promising-results-reported-for-system-monitoring-organ-motion-during-radiotherapy/#_ednref7 "_edn7") Enke CA, Solberg T, Mahadevan A, Clinical impact of 3 mm versus 5 mm action threshold for correction of intrafractional prostate motion identified with electromagnetic tracking. Proceedings of the 48th annual meeting of the American Society for Therapeutic Radiology and Oncology. November 2006;Abstract 2275, Published in the International Journal of Radiation Oncology* Biology*Physics.

[[8]](http://news.cancerconnect.com/promising-results-reported-for-system-monitoring-organ-motion-during-radiotherapy/#_ednref8 "_edn8") Jani S, Weinstein G, Kupelian P, et al. In-vivo comparison of an electromagnetic system to standard kV X-rays for treatment setup during external beam radiotherapy for patients with prostate cancer. Proceedings of the 48th annual meeting of the American Society for Therapeutic Radiology and Oncology. November 2006; Abstract 139, Published in the International Journal of Radiation Oncology* Biology*Physics.

[[9]](http://news.cancerconnect.com/promising-results-reported-for-system-monitoring-organ-motion-during-radiotherapy/#_ednref9 "_edn9") Kupelian PA, Willoughby, Mahadevan A, et al. Characterization of real time motion of the prostate gland in patients receiving external radiotherapy for localization prostate cancer: Tracking during 1157 fractions with the Calypso system. Proceedings of the 48th annual meeting of the American Society for Therapeutic Radiology and Oncology. November 2006; Abstract 139, Published in the International Journal of Radiation Oncology* Biology*Physics.

[[10]](http://news.cancerconnect.com/promising-results-reported-for-system-monitoring-organ-motion-during-radiotherapy/#_ednref10 "_edn10") Willoughby T, Kupelian P, Mahadevan A, et al. Position correction guidance utilizing real-time tracking with the Calypso® system for external beam radiation therapy delivery in patients with localized prostate cancer. Proceedings of the 48th annual meeting of the American Society for Therapeutic Radiology and Oncology. November 2006; Abstract 1136, Published in the International Journal of Radiation Oncology* Biology*Physics.

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