1. DWI-MR and PET-CT Functional Imaging for Boost Tumor Volume Delineation in Neoadjuvant Rectal Cancer Treatment
- Author
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Rosa, Consuelo, Gasparini, Lucrezia, DI Guglielmo, Fiorella Cristina, Caravatta, Luciana, DI Tommaso, Monica, Delli Pizzi, Andrea, Martino, Gianluigi, Castaldi, Paola, Mazza, Rocco, Porreca, Annamaria, DI Nicola, Marta, Calcagni, Maria Lucia, Genovesi, Domenico, Rosa, Consuelo, Gasparini, Lucrezia, DI Guglielmo, Fiorella Cristina, Caravatta, Luciana, DI Tommaso, Monica, Delli Pizzi, Andrea, Martino, Gianluigi, Castaldi, Paola, Mazza, Rocco, Porreca, Annamaria, DI Nicola, Marta, Calcagni, Maria Lucia, and Genovesi, Domenico
- Abstract
BACKGROUND/AIM T2 weighted magnetic resonance (MR) imaging is the gold standard for locally advanced rectal cancer (LARC) staging. The potential benefit of functional imaging, as diffusion-weighted MR (DWI) and positron emission tomography-computed tomography (PET-CT), could be considered for treatment intensification strategies. Dose intensification resulted in better pathological complete response (pCR) rates. This study evaluated the inter-observer agreement between two radiation oncologists, and the difference in gross tumor volume (GTV) delineation in simulation-CT, T2-MR, DWI-MR, and PET-CT in patients with LARC. PATIENTS AND METHODS Two radiation oncologists prospectively delineated GTVs of 24 patients on simul-CT (CT$_{GTV}$), T2-weighted MR (T2$_{GTV}$), echo planar b1000 DWI (DWI$_{GTV}$) and PET-CT (PET$_{GTV}$). Observers' agreement was assessed using Dice index. Kruskal-Wallis test assessed differences between methods. RESULTS Mean CT$_{GTV}$, T2$_{GTV}$, DWI$_{GTV}$, and PET$_{GTV}$ were 41.3±26.9 cc, 25.9±15.2 cc, 21±14.8 cc, and 37.7±27.7 cc for the first observer, and 42.2±27.9 cc, 27.6±16.9 cc, 19.9±14.9cc, and 34.8±24.3 cc for the second observer, respectively. Mean Dice index was 0.85 for CT$_{GTV}$, 0.84 for T2$_{GTV}$, 0.82 for DWI$_{GTV}$, and 0.89 for PET$_{GTV}$, representative of almost perfect agreement. Kruskal-Wallis test showed a statistically significant difference between methods (p=0.009). Dunn test showed there were differences between DWI$_{GTV}$ vs. PET$_{GTV}$ (p=0.040) and DWI$_{GTV}$ vs. CT$_{GTV}$ (p=0.008). CONCLUSION DWI resulted in smaller volume delineation compared to CT, T2-MR, and PET-CT functional images. Almost perfect agreements were reported for each imaging modality between two observers. DWI-MR seems to remain the optimal strategy for boost volume delineation for dose escalation in patients with LARC.
- Published
- 2023