IGRTþHDR BT was a salvage treatment after local failure of either previous I-125 brachytherapy (2 cases). There was no evidence of nodal or distant metastases at the time of treatment in all patients. Of the primary treatment group, most (42/62) patients were classified as high risk, 18/62 were intermediate risk. In 31 patients the external radiation dose administered was hypofractionated: 36 Gy given in 12 fractions. In 33 patients a standard fractionated schema (50 Gy, given in 25 fractions) was used. The HDR BT dose ranged between 9.5 and 15 Gy (median 14 Gy). In 61 patients the HDR BT was given 1 month after completion of IGRT, in 2 patients the HDR BT was given in the middle of external radiation and, in 1 case before the beginning of IGRT. The prostate dose (IGRT plus HDR BT) resulted in average biological equivalent doses O 128 Gy (a/b 5 3). 41 (64%) patients also had androgen deprivation treatment for at least 6 months. Median follow-up was 12.5 months (range 1-58). All patients completed the treatment as prescribed. 62/64 patients were alive at the time of last follow- up, 92.2 % free from biochemical relapse. Three patients had biochemical recurrence without clinical or radiologic evidence of disease and two had bone metastases progression. Acute transient GU and GI morbidity G1- G2 were seen in 45 % and 7 % of patients. Late GU and GI morbidity were seen in 8 % and 4 % of patients. No acute or late G3-G4 GU or GI morbidity was seen. There were no differences in the rate or severity of the toxicity observed between the hypofractionated and the normofractionated external radiation schemas. Conclusions: Single-dose HDR-boosted IGRT, both with standard and hypofractionation, was well tolerated in the short and medium term with low toxicity and encouraging early indicators of disease control. This treatment schema allows dose escalation and provides a high biologically effective dose. These results are in line with those observed in previous international reports, but further follow-up is necessary in order to assess overall and biochemical relapse-free survival. PO43 Stranded Seeds and Seed Displacement as Estimated By Day 0 Fluoroscopy and Four Month Post-Implant Pelvic X-Ray Brandon J. Birckhead, BS, Brian J. Davis, MD, PhD, Chris L. Deufel, PhD, Keith M. Furutani, PhD, Kenneth W. Merrell, MD, Lance A. Mynderse, MD. Mayo Clinic, Rochester, MN, USA. Purpose: Loose seed placement in permanent prostate brachytherapy (PPB) is associated with seed migration to the lung and other locations in the body whereas seed placement with stranded seeds is associated with reduced seed migration. However, some reports indicate that seed displacement of stranded seed trains in and around the prostate may occur such that prostate dosimetry is adversely affected. The purpose of this study is to examine a large series of sequential plain 2D images to determine if obvious and substantial seed displacement occurs. Materials and Methods: Between 10/2010 and 5/2014 a series of 102 patients underwent PPB at our institution who had routine post-implant fluoroscopy (PIF), Day 0 post-implant dosimetry (PID) and gold marker placement near the prostate base and apex. Since 2004, 686 patients have undergone implant with stranded seeds only and in 2011, a general policy of including pelvic in addition to chest x-rays at four month follow up visits was implemented by one of the brachytherapists. Implants routinely included seed placement in the base and apex with separate seed trains of only two or three seeds in length as opposed to seed trains traversing the entire length of the prostate. Apical seed placement was at or typically within 8 mm of the apex. In order to determine if any seed displacement occurred a comparison of the PIF taken at day zero and standing pelvic image four months later using the gold seed length of 3 mm as the reference length. Measurements and observations include: 1) an X-axis measurement (horizontal) measuring the distances between the two furthest seeds in that direction. 2) Y-axis measurement (vertical) with seeds measurement including distance between gold seeds, superior seed and inferior seed from the gold seed placement. A total of 102 cases were available for analysis. Results: The Y-axis distance of day 0 Fluoroscopy images (range:38mm- 81mm), and four month standing pelvic x-ray (range: 34mm-106mm). The mean for Day 0 Y-axis distance was 54mm and the mean for the 4 month Y-axis distance was 52mm. The X-axis distance of day 0 Fluoroscopy image was (range 33mm-66mm), and the four month standing x-ray image (range: 45mm-76mm). The mean for Day 0 X-axis distance was 51mm and for the 4 month mean X-axis distance was 59mm. One patient lost 10 seeds through apparent seed migration through the bladder and urethra with no apparent adverse clinical consequences. Four patients had significant local migration of 1 or 2 seeds from the prostate, 3 moved superior to the prostate and 1 inferior to the prostate. 3 patients also had migration of seeds to the chest. Conclusions: Despite the limitations evident in method employed in this study comparing two disparate plain imaging techniques (PIF vs pelvic x- ray) with different source to subject distance, and patients in different positions (extended dorsal lithotomy and standing), some general observations are possible: 1) no repetitive or systematic loss of seeds through the bladder or urethra occurred, 2) no seed displacement in the caudal direction appeared routinely, 3) technique-related factors may explain the finding in this study as compared to prior reports, and 4) sequential CT or MR-based dosimetry is necessary in order to further substantiate these findings. PO44 A Retrospective Review of 366 Patients Treated With LDR Prostate Brachytherapy at a Single Institution: Histopathologic, Biochemical, and Dosimetric Predictors of Outcome Omar Y. Mian, MD, PhD, Scott P. Robertson, PhD, Amol Narang, MD, Hee Joon Bae, BS, Phuoc Tran, MD, PhD, Theodore L. DeWeese, MD, Danny Song, MD. Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins Hospital, Baltimore, MD, USA. Purpose: Biochemical control and patient reported quality of life outcomes for 366 patients treated with LDR permanent prostate seed brachytherapy between 2004 and 2014 at a single institution are reported. Materials and Methods: 366 patients with stage cT1-T2 prostate cancer received permanent LDR prostate brachytherapy over a 10 year interval at a single institution. Pd-103 seed implantation was performed using ultrasound-based localization. Standard dosimetric parameters for implant quality and safety were recorded. PSA was determined and patients completed a QoL instrument (Expanded Prostate Cancer Index Composite, EPIC) prior to treatment and at each follow-up. Kaplan-Meier estimates of biochemical failure as defined by Phoenix criteria were S98 Abstracts / Brachytherapy 14 (2015) S11–S106