Interobserver variation in clinical target volume (CTV) delineation for stereotactic radiotherapy to non-spinal bone metastases in prostate cancer: CT, MRI and PET/CT fusion. (March 2023)

• Record Type: Journal Article
• Authors: Chapman, Ewan Richard; Nicholls, Luke; Suh, Yae-Eun; Khoo, Vincent; Levine, Daniel; ap Dafydd, Derfel; Van As, Nicholas
• Is Part Of: Radiotherapy and oncology. Volume 180(2023)
• Publication Date: 2023-03
• Subjects: SABR -- Bone metastases -- Inter-observer variability -- MRI -- PET/CT; Oncology -- Periodicals; Radiotherapy -- Periodicals; Tumors -- Periodicals; Medical Oncology -- Periodicals; Neoplasms -- radiotherapy -- Periodicals; Radiotherapy -- Periodicals; Radiothérapie -- Périodiques; Cancérologie -- Périodiques; Tumeurs -- Périodiques; Electronic journals; 616.9940642
• DOI: 10.1016/j.radonc.2022.109461
• Languages: English
• ISSNs: 0167-8140

Abstract

Highlights: MRI fusion alone does not significantly impact inter-observer variability in the delineation of prostate cancer bone metastases. Significant improvements in inter-observer variability were seen with PET-CT fusion with planning CT. Dual fusion with both PET-CT and MRI significantly increased delineated volumes of bone metastases and improved inter-observer variability as compared to MRI fusion and planning CT alone. Abstract: Background and purpose: The use of SBRT for the treatment of oligometastatic prostate cancer is increasing rapidly. While consensus guidelines are available for non-spinal bone metastases practice continues to vary widely. The aim of this study is to look at inter-observer variability in the contouring of prostate cancer non-spinal bone metastases with different imaging modalities. Materials and methods: 15 metastases from 13 patients treated at our centre were selected. 4 observers independently contoured clinical target volumes (CTV) on planning CT alone, planning CT with MRI fusion, planning CT with PET-CT fusion and planning CT with both MRI and PET-CT fusion combined. The mean inter-observer agreement on each modality was compared by measuring the delineated volume, generalized conformity index (CIgen), and the distance of the centre of mass (dCOM), calculated per metastasis and imaging modality. Results: Mean CTV volume delineated on planning CT with MRI and PET-CT fusion combined was significantly larger compared to other imaging modalities (p = 0.0001). CIgen showed marked variation between modalities with the highest agreement between planning CT + PET-CT (mean CIgen 0.55, range 0.32–0.73) and planning CT + MRI + PET-CT (mean CIgen 0.59, range 0.34–0.73). dCOM showed small variations between imaging modalities but a significantly shorter distance found on planning CT + PET-CT when compared with planning CT + PET-CT + MRI combined (p = 0.03). Conclusions: Highest consistency in CTV delineation between observers was seen with planning CT + PET-CT and planning CT + PET-CT + MRI combined.