Unexpected Seed Migration in Prostate Brachytherapy Implants Coincident with Change in Seed Stranding Product.

Jim Rose,Don Yee,Oleksandr Boychak,John Amanie,Albert Murtha,Ron Sloboda,Nawaid Usmani,Nadeem Pervez,Derek Liu

doi:10.7759/cureus.1243

Abstract

Purpose: This study was undertaken to determine if significant seed migration occurred when our institution changed seed products by comparing patterns of seed migration in implants containing different stranding material.Methods and Materials: Day 0 and Day 30 CT scans were registered by the contoured prostate center of mass. An implant reconstruction program identified seeds on CT according to the pre-plan, enabling one-to-one correspondence between Day 0 and Day 30 seeds. Significant seed migration was defined by review of seeds that migrated > 2 cm outside the prostate or appearance in unexpected locations. Results: Twenty-five (149, 16.8%) new strands displayed movement > 2 cm between Day 0 and Day 30 compared with just 2/118 (1.7%) of the standard strands. Six out of 26 (23%) patients with new strands displayed significant migration compared with 2/13 (14%) of patients with standard strands. In the six patients with new strands and significant migration, a mean of four strands (17%, range: 2-8 per patient) migrated significantly with 65% due to whole strand migration, 25% due to strand breakage, and 10% strand clumping. In the control group, only two strands (2%) migrated significantly, both due to strand breakage. Despite the greater seed movement with the new strands, Day 0 and Day 30 dosimetry was acceptable.Conclusion: In this short report, we identified that a change to a new strand type was associated with unexpected significant seed movement compared to our typical strands. Since seed movement can arise from unexpected causes, it is important to maintain quality assurance practices when a change in technique or infrastructure is instituted.

Highlights

Low dose rate (LDR) permanent seed prostate brachytherapy is an established curative treatment for men with favorable-risk prostate cancer
The success of treatment depends on patient risk factors and implant quality, the latter that is assessed with postoperative dosimetry involving computed tomography (CT) and magnetic resonance imaging (MRI) up to 30 days post-implant [1,2,3]
After returning to our standard strands, a further 14 consecutive patients were implanted with only two patients showing the migration of a single strand > 2 cm beyond the prostate (2/340 (0.6%) strands implanted). These six patients implanted with the new strands that displayed significant strand migration were compared with a series of five patients matched with similar operative characteristics implanted after we returned to the standard stranding product

Summary

Introduction

Low dose rate (LDR) permanent seed prostate brachytherapy is an established curative treatment for men with favorable-risk prostate cancer. The success of treatment depends on patient risk factors and implant quality, the latter that is assessed with postoperative dosimetry involving computed tomography (CT) and magnetic resonance imaging (MRI) up to 30 days post-implant [1,2,3]. Factors that may influence seed migration include the use of stranded vs loose seeds, planning algorithm, the length of the seed train, use of sagittal imaging, urethral contrast, and others [6,7,8]

Methods

Results

Discussion

Conclusion