Impact of hydrogel peri-rectal spacer insertion on prostate gland intra-fraction motion during 1.5 T MR-guided stereotactic body radiotherapy

• DOI: 10.1186/s13014-020-01622-3
• Publication Date: 2020-07-22T12:03:38Z
• Authors: Francesco Cuccia; Rosario Mazzola; Luca Nicosia; Vanessa Figlia; Niccolò Giaj-Levra; Francesco Ricchetti; Michele Rigo; Claudio Vitale; Beatrice Mantoan; Antonio De Simone; Gianluisa Sicignano; Ruggero Ruggieri; Stefano Cavalleri; Filippo Alongi
• Keywords: Male; Organs at Risk; Stereotactic body radiotherapy; R895-920; Radiosurgery; Medical physics. Medical radiology. Nuclear medicine; Motion; 03 medical and health sciences; 0302 clinical medicine; Humans; Organ motion; Mri-linac; Organ motion; Prostate cancer; Stereotactic body radiotherapy; RC254-282; Aged; Prostate cancer; Research; Radiotherapy Planning, Computer-Assisted; Rectum; Neoplasms. Tumors. Oncology. Including cancer and carcinogens; Prostatic Neoplasms; Hydrogels; Radiotherapy Dosage; Mri-linac; Middle Aged; Magnetic Resonance Imaging; 3. Good health; Radiotherapy, Image-Guided

Abstract Background The assessment of organ motion is a crucial feature for prostate stereotactic body radiotherapy (SBRT). Rectal spacer may represent helpful device in order to outdistance rectal wall from clinical target, but its impact on still matter debate. MRI-Linac new frontier radiation oncology as it allows superior visualization the real-time anatomy patient and current highest level adaptive radiotherapy. Methods We present data regarding total 100 fractions 20 patients who underwent MRI-guided SBRT low-to-intermediate risk cancer with or without spacer. Translational rotational shifts were computed pre- post-treatment MRI acquisitions referring delivery position antero-posterior, latero-lateral cranio-caudal direction, assessed using Mann-Whitney U-Test. Results All treated five sessions schedule (35 Gy/5fx) median fraction treatment time 50 min (range, 46–65). In entire study sample, displacement was 0.1° cranio-caudal, − 0.002° 0.01° antero-posterior direction; translational shift 0.11 mm 0.24 0.22 antero-posterior. A significant difference between no-spacer terms direction ( p = 0.033) observed; also positive trend detected 0.07), although no statistical significance. observed statistically differences pre-treatment planning phase favor cohort several rectum dose constraints: V32Gy < 5% 0.001), V28 Gy 10% 0.001) V18Gy 35% 0.039). Also bladder V35 1 cc, use provided dosimetric advantage compared subpopulation 0.04). Furthermore, PTV V33.2Gy > 95% higher one 0.036). Conclusion our experience, application hydrogel resulted contributing limit intra-fraction motion. Further studies larger sample size longer follow-up are required confirm this ideally favorable effect assess any potential outcomes.