Stability of Intraprostatic Electromagnetic Transponders in Patients Receiving Radiation Therapy, Wi

1
Stability of Intraprostatic Electromagnetic
Transponders in Patients Receiving Radiation
Therapy, With and Without Neoadjuvant and/or
Concurrent Androgen Suppression Therapy
G. Weinstein1, S. Jani1, P. Kupelian2, T.
Willoughby2, C. Enke3, T. Solberg3, N.
Flores4, D. Liu4, A. Mahadevan5, T.
Djemil5 1Sharp Memorial Hospital, San Diego, CA,
2M.D. Anderson Cancer Center Orlando, Orlando,
FL, 3Nebraska Medical Center, Omaha, NE,
4Scottsdale Healthcare/Arizona Oncology Services,
Scottsdale, AZ, 5Cleveland Clinic, Cleveland, OH
Purpose/Objectives
Results (continued)
Methods
Forty-one (41) patients participated in a
clinical study under an IDE to evaluate utility
of electromagnetic transponders as markers to
localize and monitor the position of the prostate
daily with external beam radiotherapy. The
transponders have an electrical circuit and are
hermetically sealed in a biocompatible glass
capsule (1.8 mm diameter x 8.6 mm). Three
electromagnetic transponders (Calypso Medical)
were placed within the prostate gland (a
transponder in the apex A, right lobe R, and
left lobe L). Thirteen (13) of the 41 (32)
patients received androgen suppression therapy
(AST). Six patients received AST (for 16 months)
before starting radiation, while seven patients
received AST both before (for 14 months) and
Intraprostatic fiducial markers may be used to
localize the prostate for delivery of external
beam radiation therapy (RT). The reliability of
this technique is dependent upon a stable
geometry of markers within the prostate to
accurately reflect the prostates position.
Since androgen suppression therapy (AST) may
reduce the prostate volume, marker geometry may
subsequently change. This analysis compares the
stability of electromagnetic transponders within
the prostate in patients treated with and without
neoadjuvant concurrent androgen suppression
therapy.
Results The total mean standard deviation of
intertransponder distance for the entire group
(n41) was 0.7 mm apex-to left (A-L), 0.7 mm
left-right (L-R), and 0.8 mm right-apex (R-A).
Corresponding values for the patients receiving
AST were 0.8 mm A-L, 0.7 mm L-R, and 0.7 mm R-A,
and for patients who did not receive AST 0.7 mm
A-L, 0.7 mm L-R, and 0.8 mm R-A.
during radiation. A CT of the prostate gland was
obtained on all patients approximately four days
following implant. Transponder coordinates were
obtained from the CT scans and used to compute
the distance between any two transponders. Daily
transponder coordinates were also obtained using
an external electromagnetic detector array
(Calypso 4D Localization System) over the full
course of RT. Intertransponder distance (a
measure of transponder stability) from 4 days
post-implant through the end of RT was compared
in the groups treated with and without AST.
Figure 4. Transponder implantation pattern (left
base, right base and apex).
Results
Conclusions
Conclusions Implanted electromagnetic
transponder markers maintain a stable geometry
within the prostate gland over time in patients
treated with AST and in patients treated with
radiation therapy alone, consistent with gold
fiducial markers used with x-rays for
localization. The electromagnetic markers also
provide continuous monitoring of the prostate
throughout treatment delivery without added
ionizing radiation.
Presented at American Society for Therapeutics
and Radiology Oncology (ASTRO), Philadelphia, PA
(November 5-9, 2006) This work was supported
through grants from Calypso Medical
Technologies, Seattle, Washington. 510(k) FDA
Cleared 2006. Not for sale outside of U.S.