TY - JOUR
T1 - Impact of endorectal filling on interobserver variability of MRI based rectal primary tumor delineation
AU - Lo Russo, Monica
AU - Nachbar, Marcel
AU - Barry, Aisling
AU - Bhide, Shree
AU - Chang, Amy
AU - Hall, William
AU - Intven, Martijn
AU - Marijnen, Corrie
AU - Peters, Femke
AU - Minsky, Bruce
AU - Romesser, Paul B.
AU - Sarkar, Reith
AU - Tan, Alex
AU - Boeke, Simon
AU - Wegener, Daniel
AU - Butzer, Sarah
AU - Boldt, Jessica
AU - Gatidis, Sergios
AU - Nikolaou, Konstantin
AU - Thorwarth, Daniela
AU - Zips, Daniel
AU - Gani, Cihan
N1 - Publisher Copyright:
© 2022 The Author(s)
PY - 2023/1
Y1 - 2023/1
N2 - Background: Online adaptive MR-guided radiotherapy allows for the reduction of safety margins in dose escalated treatment of rectal tumors. With the use of smaller margins, precise tumor delineation becomes more critical. In the present study we investigated the impact of rectal ultrasound gel filling on interobserver variability in delineation of primary rectal tumor volumes. Methods: Six patients with locally advanced rectal cancer were scanned on a 1.5 T MRI-Linac without (MRI_e) and with application of 100 cc of ultrasound gel transanally (MRI_f). Eight international radiation oncologists expert in the treatment of gastrointestinal cancers delineated the gross tumor volume (GTV) on both MRI scans. MRI_f scans were provided to the participating centers after MRI_e scans had been returned. Interobserver variability was analyzed by either comparing the observers’ delineations with a reference delineation (approach 1) and by building all possible pairs between observers (approach 2). Dice Similarity Index (DICE) and 95 % Hausdorff-Distance (95 %HD) were calculated. Results: Rectal ultrasound gel filling was well tolerated by all patients. Overall, interobserver agreement was superior in MRI_f scans based on median DICE (0.81 vs 0.74, p < 0.005 for approach 1 and 0.76 vs 0.64, p < 0.0001 for approach 2) and 95 %HD (6.9 mm vs 4.2 mm for approach 1, p = 0.04 and 8.9 mm vs 6.1 mm, p = 0.04 for approach 2). Delineated median tumor volumes and inter-quartile ranges were 26.99 cc [18.01–50.34 cc] in MRI_e and 44.20 [19.72–61.59 cc] in MRI_f scans respectively, p = 0.012. Conclusions: Although limited by the small number of patients, in this study the application of rectal ultrasound gel resulted in higher interobserver agreement in rectal GTV delineation. The endorectal gel filling might be a useful tool for future dose escalation strategies.
AB - Background: Online adaptive MR-guided radiotherapy allows for the reduction of safety margins in dose escalated treatment of rectal tumors. With the use of smaller margins, precise tumor delineation becomes more critical. In the present study we investigated the impact of rectal ultrasound gel filling on interobserver variability in delineation of primary rectal tumor volumes. Methods: Six patients with locally advanced rectal cancer were scanned on a 1.5 T MRI-Linac without (MRI_e) and with application of 100 cc of ultrasound gel transanally (MRI_f). Eight international radiation oncologists expert in the treatment of gastrointestinal cancers delineated the gross tumor volume (GTV) on both MRI scans. MRI_f scans were provided to the participating centers after MRI_e scans had been returned. Interobserver variability was analyzed by either comparing the observers’ delineations with a reference delineation (approach 1) and by building all possible pairs between observers (approach 2). Dice Similarity Index (DICE) and 95 % Hausdorff-Distance (95 %HD) were calculated. Results: Rectal ultrasound gel filling was well tolerated by all patients. Overall, interobserver agreement was superior in MRI_f scans based on median DICE (0.81 vs 0.74, p < 0.005 for approach 1 and 0.76 vs 0.64, p < 0.0001 for approach 2) and 95 %HD (6.9 mm vs 4.2 mm for approach 1, p = 0.04 and 8.9 mm vs 6.1 mm, p = 0.04 for approach 2). Delineated median tumor volumes and inter-quartile ranges were 26.99 cc [18.01–50.34 cc] in MRI_e and 44.20 [19.72–61.59 cc] in MRI_f scans respectively, p = 0.012. Conclusions: Although limited by the small number of patients, in this study the application of rectal ultrasound gel resulted in higher interobserver agreement in rectal GTV delineation. The endorectal gel filling might be a useful tool for future dose escalation strategies.
KW - Inter-observer agreement
KW - MR-guided radiotherapy
KW - MRI-Linac
KW - Rectal cancer
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U2 - 10.1016/j.ctro.2022.09.002
DO - 10.1016/j.ctro.2022.09.002
M3 - Article
C2 - 36299279
AN - SCOPUS:85140066911
SN - 2405-6308
VL - 38
SP - 1
EP - 5
JO - Clinical and Translational Radiation Oncology
JF - Clinical and Translational Radiation Oncology
ER -