Magnetic resonance imaging (MRI) compared with computed tomography (CT) for interobserver agreement of gross tumor volume delineation in pancreatic cancer: a multi-institutional contouring study on behalf of the AIRO group for gastrointestinal cancers

Abstract

Genovesi (2019) Magnetic resonance imaging (MRI) compared with computed tomography (CT) for interobserver agreement of gross tumor volume delineation in pancreatic cancer: a multiinstitutional contouring study on behalf of the AIRO group for gastrointestinal cancers, Acta Oncologica, 58:4, 439-447, ABSTRACT Background: Due to the high soft tissue resolution, magnetic resonance imaging (MRI) could improve the accuracy of pancreatic tumor delineation in radiation treatment planning. A multi-institutional study was proposed to evaluate the impact of MRI on inter-observer agreement in gross tumor volume (GTV) and duodenum delineation for pancreatic cancer compared with computer tomography (CT). Material and Methods: Two clinical cases of borderline resectable (Case 1) and unresectable (Case 2) pancreatic cancer were selected. In two sequential steps, diagnostic contrast-enhanced CT scan and MRI sequences were sent to the participating centers. CT-GTVs were contoured while blinded to MRI data sets. DICE index was used to evaluate the spatial overlap accuracy. Results: Thirty-one radiation oncologists from different Institutions submitted the delineated volumes. CT-and MRI-GTV mean volumes were 21.6 ± 9.0 cm 3 and 17.2 ± 6.0 cm 3 , respectively for Case 1, and 31.3 ± 15.6 cm 3 and 33.2 ± 20.2 cm 3 , respectively for Case 2. Resulting MRI-GTV mean volume was significantly smaller than CT-GTV in the borderline resectable case (p < .05). A substantial agreement was shown by the median DICE index for CT-and MRI-GTV resulting as 0.74 (IQR: 0.67-0.75) and 0.61 (IQR: 0.57-0.67) for Case 1; a moderate agreement was instead reported for Case 2: 0.59 (IQR:0.52-0.66) and 0.53 (IQR:0.42-0.62) for CT-and MRI-GTV, respectively. Conclusion: Diagnostic MRI resulted in smaller GTV in borderline resectable case with a substantial agreement between observers, and was comparable to CT scan in interobserver variability, in both cases. The greater variability in the unresectable case underlines the critical issues related to the outlining when vascular structures are more involved. The integration of MRI with contrast-enhancement CT, thanks to its high definition of tumor relationship with neighboring vessels, could offer a greater accuracy of target delineation.

Basics and Frontiers on Pancreatic Cancer for Radiation Oncology: Target Delineation, SBRT, SIB Technique, MRgRT, Particle Therapy, Immunotherapy and Clinical Guidelines

“…This study confirmed that a smaller GTV is delineated on MRI compared with CTscan in the case of BRPC. On the other hand, a large contouring variability was reported in LAPC cases, suggesting that the tumor area close to vascular structures or involving them should be considered as a region of complex anatomy for GTV delineation, requiring very accurate guidelines for volume definition and confirming the results of previous studies [70,71] and as also highlighted by the expert panel of the international contouring conference [69].…”

Training and validation of a robust PET radiomic-based index to predict distant-relapse-free-survival after radio-chemotherapy for locally advanced pancreatic cancer

“…Of note, the authors found a 7-variable radiomic index to predict OS, mostly related to intra-tumor heterogeneity, in part consistent with the finding regarding COMshift. Differently from our study, in Cui et al GTV was delineated on CT and overlayed on PET without any PET segmentation; moreover, the impact of inter-observer variability was simply assessed by rigidly modifying contours and looking to the changes induced in the features, which is a rough approximation of the true inter-observer variability reported for TC [37]. In our opinion, this method, together with the no-IBSI compliance of the used software at that time, makes their findings poorly generalizable.…”

Impact of FAPI-PET/CT on Target Volume Definition in Radiation Therapy of Locally Recurrent Pancreatic Cancer

“…In our study, this inconsistency is revealed by the low DSC range of 0.55 to 0.65. A previous study of unresected pancreatic cancer cases by Caravatta et al reported CTbased DSCs of 0.59 and 0.74 [22]. Recently, van der Veen et al observed DSCs of 0.51 to 0.79 in head and neck cancer target definition [23].…”