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Proposed Hydrogel-Implant-Quality-Score (HIQS) and a Matched-Pair Study for Prostate Radiotherapy

H Liu1*, L Borden2 , D Wiant3 , B Sintay4 , T Hayes5 , H Woodruff6 , M Manning7 , (1) Cone Health Cancer Center, Greensboro, NC, (2) Alliance Urology, Greensboro, NC ,(3) Cone Health Cancer Center, Greensboro, NC, (4) Cone Health Cancer Center, Greensboro, NC, (5) Cone Health Cancer Center, Greensboro, NC, (6) Cone Health Cancer Center, Greensboro, NC,(7) Cone Health Cancer Center, Greensboro, NC


(Sunday, 7/14/2019)  

Room: ePoster Forums

Purpose: Hydrogel spacer (SpaceOAR) has been used to reduce rectal toxicity in prostate radiotherapy. The present study aims to develop a Hydrogel-Implant-Quality-Score (HIQS) system to assist clinicians in tracking proficiency and to support quality improvement; and design a matched-pair study for LDR patients to investigate the benefit of SpaceOAR in rectal dose reduction.

Methods: 55 patients (IMRT and/or LDR) were respectively selected. Each patient had SpaceOAR implantation under manufacturer supervision. Post-procedure CT and T2-MRI were acquired for planning. A novel scoring system was proposed to evaluate the hydrogel placement quality with criteria including implanted hydrogel volume, left-right symmetry, cranio-caudal symmetry and mid-prostate spacing. Hydrogel implantation was done immediately after LDR seed placement. For each LDR patient (total of 35 patients), a non-SpaceOAR patient was matched based upon intra-operative plan rectal dose (D2cc and D0.1cc) and prostate coverage (V100, V150 and V200). The rectal dose reduction of intra-operative and post-operative were compared between spaceOAR and non-spaceOAR groups using the Student’s t-test.

Results: The average hydrogel volume and mid-prostate spacing were 13.5±2.3cc and 14.6±3.4mm. The mean HIQS were 77.5±13.0. Rectal anatomical distortions, including disruption of serosal and/or submucosal layers, were seen in 14 cases. HIQS was higher in patients without rectal distortion compared with patients with rectal distortion: 79.7±9.3 vs. 71.0±19.4. Over the duration of the practice HIQS improved with a linear trend from 74 to 82 suggesting improved quality with experience. Significant rectal dose reductions between intra-operative and post-operative plans were found for SpaceOAR patients compared to non-SpaceOAR patients (D2cc: 24.1±13.6Gy vs. -6.2±19.1Gy; D0.1cc: 59.2±26.9Gy vs. 13.3±25.1Gy).

Conclusion: HIQS quantifies hydrogel placement quality and provides insights into clinician’s learning and DVH outcome. Larger samples will be needed for validation of HIQS. This study will contribute to a safety culture around quality in SpaceOAR implantation to reduce the likelihood of severe complications.


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