S334 I. J. Radiation Oncology d Biology d Physics Volume 72, Number 1, Supplement, 2008

2368 Pre-biopsy Prostate-specific Antigen Velocity does not Predict Gleason Score, Tumor Location or Cancer

Volume Following Transperineal-template Guided Prostate Mapping Biopsy: Implications for ProstateBrachytherapy Treatment Planning

N. Bittner1, G. S. Merrick2, K. E. Wallner3, W. M. Butler2, R. L. Anderson2, Z. A. Allen2, E. Adamovich4

1University of Washington, Seattle, WA, 2Schiffler Cancer Center, Wheeling, WV, 3Puget Sound Healthcare Corporation,Seattle, WA, 4Wheeling Hospital, Dept of Pathology, Wheeling, WV

Purpose/Objective(s): Prostate-specific (PSA) velocity (PSAV) is associated with higher pathologic Gleason scores and greaterprostate cancer mortality. In this study, we evaluated the impact of PSAV on prostate cancer diagnosis, Gleason score, tumor lo-cation and cancer volume in men undergoing transperineal template-guided mapping biopsy (TTMB).

Materials/Methods: From January 2005 through September 2007, 217 patients underwent TTMB. Criteria for inclusion includeda persistently elevated PSA and/or the diagnosis of ASAP or high-grade PIN on prior biopsy. The prostate gland was arbitrarilydivided into 24 regions and a median of 56 biopsies were obtained per patient. Patients were divided into 3 velocity cohorts by thefollowing change in PSA diagnosis in the year prior to biopsy: # 0.0 ng/mL, 0.1 - 1.9 ng/mL and $2.0 ng/mL. Multiple parametersincluding PSAV were evaluated as predictors for prostate cancer diagnosis, Gleason score, tumor volume and cancer location.

Results: The mean patient age was 64.5 years with a mean pre-biopsy PSA of 8.3. Prostate cancer was diagnosed in 124 patients(50.6%). When stratified by PSAV, an increase of $2.0 ng/mL was statistically associated with older age, a higher pre-biopsy PSA,a higher PSA density, a greater transition zone index, and were least likely to have a prior biopsy diagnosis of ASAP or PIN. Noother differences were discerned between the 3 cohorts. PSAV did not predict for prostate cancer diagnosis (p = 0.317), Gleasonscore (p = 0.757), the number of positive cores (p = 0.083) or tumor location (p = 0.423). In multivariate analysis, prostate cancerdiagnosis was best predicted by pre-biopsy diagnosis, the total number of prior biopsy cores and the transition zone. Gleason scorewas best predicted by transition zone volume, while prostate cancer volume was most closely related to patient age, total biopsycores and the transition zone. PSAV did not predict for any of the evaluated parameters.

Conclusions: In patients undergoing transperineal template-guided mapping biopsy, pre-biopsy PSAV did not correlate with pros-tate cancer, grade, volume or location. Although in prostate brachytherapy patients, supplemental external beam radiation therapyto the pelvic lymph nodes and/or androgen deprivation therapy may be indicated in patients with a greater PSAV, intraprostaticbrachytherapy dose distributions should not be altered.

Author Disclosure: N. Bittner, None; G.S. Merrick, None; K.E. Wallner, None; W.M. Butler, None; R.L. Anderson, None; Z.A.Allen, None; E. Adamovich, None.

2369 Quantifying Respiratory-induced Prostate Motion using Continuous Real-time Tracking Technology

T. L. McDonald, L. Ku, K. M. O’Donnell, D. Kaurin, P. J. Gagnon, C. R. Thomas, A. Y. Hung, M. Fuss

Oregon Health & Science University, Portland, OR

Purpose/Objective(s): Prostate positional variability can alter the effectiveness of radiation therapy when precise target location isunknown. Traditionally, PTV margins are designed to compensate for inter-fraction prostate setup variability. PTV margins may bereduced when using daily image-guidance. More recently, the dosimetric relevance of intra-fraction prostate motion has been rec-ognized, and may be compensated for by continuous real-time adaptive radiation therapy afforded by the Calypso 4D LocalizationSystem�. As of today, sparse data is available regarding the magnitude and clinical relevance of high-frequency respiratory-in-duced prostate motion. The specific aim of this analysis was to quantify respiratory-induced prostate motion using electromagneticcontinuous real-time tracking technology.

Materials/Methods: In twenty patients, prostate motion during radiation delivery was measured using the Calypso System. Prior toradiotherapy planning, three beacon transponders were implanted in the prostate and used for daily localization and continuous real-time positional tracking. Motion tracking reports were generated electronically. Respiratory motion was cross-verified using theclinically tested Varian Real Time Position Management System� (RPM system). Four hundred fifty motion traces were analyzed.

Results: Ninety-five percent of analyzed real-time motion tracking traces demonstrated identifiable respiratory-induced prostatemotion (high-frequency motion .0.5 mm). The observed frequency of respiration motion correlated with the respiration frequencyderived from the RPM system. The frequency and magnitude of prostate respiratory motion was found to be patient specific andrelatively consistent over a course of external beam radiation. Cranio-caudal prostate respiration motion was largest, followed byanterior-posterior movement. Respiratory-induced lateral motion never exceeded 0.5 mm. In 14 patients respiratory-induced pros-tate motion exceeded 1 mm over 75% of the time (mean 1.3 mm). The largest measured amplitude of respiratory motion was 2.5 mm.

Conclusions: Electromagnetic prostate positional tracking during continuous real-time adaptive radiation therapy delivery allowedidentifying respiratory-induced high-frequency intra-fraction prostate motion. The observed respiratory-induced motion was largerthan previously reported in the literature, where maximum motion of less than 1 mm was described. While the observed motion wassmall relative to the inter-fraction setup variability of the prostate, individual respiratory-related prostate motion of up to 2.5 mmshould be considered when using very narrow PTV safety margins for prostate external beam radiation treatment.

Author Disclosure: T.L. McDonald, None; L. Ku, None; K.M. O’Donnell, None; D. Kaurin, None; P.J. Gagnon, None; C.R.Thomas, None; A.Y. Hung, None; M. Fuss, None.

2370 High Dose Rate Brachytherapy Boost for Prostate Cancer: Comparison of Two Different Fractionation

Schemes

T. Kaprealian, V. Weinberg, J. Speight, A. R. Gottschalk, M. Roach III, K. Shinohara, I. J. Hsu

University of California San Francisco, San Francisco, CA

Purpose/Objective(s): A retrospective review of our experience and outcomes using high-dose-rate (HDR) brachytherapy boostfor prostate cancer comparing two different fractionation schemes: 600 cGy x 3 (Group 1) compared with 950 cGy x 2 (Group 2).