Oral and Poster Presentation – Physics Abstracts Archive

UK & Ireland Prostate Brachytherapy Conference 2017

Abstract number 7

Review and optimisation of Seed Migration detection following LDR permanent prostate loose seed implants

Day K*; Awunor O*; Doggart A*; O’Donnell H*; Rogers P*; Baker C*
*Royal Berkshire Hospital NHS Foundation Trust

AIMS/INTRODUCTION: Low dose rate (LDR) permanent seed implantation is associated with a risk of seed migration (SM) and subsequent embolisation (SE), which is most likely to occur in the pulmonary vasculature1, with an average rate of 25% (range 10-55%)2. The potential for adverse dosimetric or clinical sequelae effects resulting from SE3,4, highlight the importance of patient pathway optimisation. Consequently, a large cohort of LDR prostate brachytherapy patients, at a single UK centre, was reviewed.

MATERIALS/METHODS: Treatment pathway data from 503 patients implanted with loose
125I seeds (STM1251, BARD – USA) were retrospectively reviewed, with seed loss (SL) and SM rates quantiﬁ ed. SL was determined from post-implant ward monitoring. SM rates were quantiﬁ ed from seed count mismatch (SCM) between the total number of Implanted Seeds (IS), the post-implant Pelvic X-Rays (PXR) and the 1 month follow-up Post-Implant Dosimetry (PID) CT scan. SM was assumed to have occurred if any seed was undetected in the PXR / PID images. SE was assessed from review of available post treatment images.

RESULTS: SL was observed to be 0.1% of the total number of implanted seeds. 80 patients (15.9%) were identiﬁ ed as SM candidates. 48(9.5%) were identiﬁ ed from IS/PXR and 57(11.3%) from IS/PID, with 25(4.9%) common to both. SCM in the remaining 23(4.6%) and 32(6.4%) patients from IS/PXR and IS/PID respectively were due to differences in PXR/PID image acquisition ﬁ eld of view, PXR image angulations, post-PXR SL and SM, and false positives. Of the 80 SM candidates, 23 had post treatment images available, with 11 showing conﬁ rmed SE – 8(thorax), 2(pelvis) and 1(abdomen).

CONCLUSION: The observed SM rates were within levels reported by other studies. Further optimisation of the PXR and PID imaging protocols may be required to improve accuracy in SM detection rates. This could potentially beneﬁ t patients with pre-implant contraindications by determining appropriate post-implant care. References: