Proposed Hydrogel Implant Quality Score (HIQS) for Prostate Radiotherapy

Abstract

A hydrogel spacer has been FDA-approved to reduce rectal toxicity in prostate radiotherapy. Training and certification for this procedure is currently performed by the manufacturer, without independent measures of quality. The technique has been associated with toxicity including rectal fistula. While quality has not reported, variability in spacing and distribution is described by clinicians. In the absence of validated instruments, the wider implementation of hydrogel spacer implants may lead to an emergence in unexpected complications creating negative consequences for the field of radiation oncology. The purpose of the current retrospective clinical study is to develop a simple robust Hydrogel Implant Quality Score (HIQS) system as a quality surrogate to assist clinicians in tracking proficiency and to support quality improvement. Between May 2018 and February 2019, 50 subjects with prostate cancer, undergoing IMRT and/or LDR brachytherapy, had hydrogel spacer implantation under standard supervision and certification from the manufacturer. No acute complications were noted. Post-procedure CT simulation and T2 MRI were performed for radiation planning. Prostate and rectal dosimetry were performed and qualitatively analyzed to identify hydrogel placement characteristics influencing dosimetry. A novel scoring system was created with criteria domains including implanted hydrogel volume, left-right symmetry (LR), cranio-caudad symmetry (CC), mid prostate spacing, distortion of prostate anatomy and distortion of rectal anatomy. HIQS scores were calculated for the patients in the series and domains were analyzed for influence on hydrogel placement quality. The average hydrogel spacer volume was 16.3 cc (SD=2.7 cc). The average mid-prostate spacing was 14.2 mm (SD=3.4 mm). Rectal anatomical distortions, including disruption of serosal and/or submucosal layers, was seen in 12 cases (24%). Overall, the HIQS ranged from 43-92 with an average of 78.5 (std dev=9.8). The HIQS was higher in patients without rectal distortion, 80 vs. 74 (NS). The HIQS was also higher with implant volume greater than 15 mL, 81 vs. 73 (NS). Over the duration of the clinical series the HIQS improved with a linear trend from 74 to 82 suggesting improved quality with experience. The current study used retrospective data to propose a universal scoring system. In ongoing work, the HIQS will require larger samples for possible validation as a predictive instrument. The HIQS suggests a risk for rectal anatomy distortion despite careful final needle position implicating needle trauma to the rectal layers during pre-implantation position adjustments. This study and contribute to a safety culture around quality in hydrogel spacer implants to reduce the likelihood of severe complications.Abstract 2672; Table 1Score(Volume)Score (LR)Score (CC)Score(spacing)Total HIQSAverage16.314.814.414.278.5Standard Deviation2.74.64.93.49.8 Open table in a new tab