Post-Neoadjuvant Chemoradiotherapy Tumor Volume Delineation Using MRI:Agreement On Volumes Between Observers

Objective:The difference of GTV delineated by the doctors from Department of Radiology and from Department of Radiotherapy was compared under MRI image sequences after neoadjuvant chemoradioth erapy for local advanced rectum cancer.And its conclusion could be used to guide GTV delineation to make it more precise under those MRI image sequences and those kinds of doctors during late-course high-dose radiotherapy for rectal cancer.Materials and Methodology:9 patients with locally advanced middle and low rectal cancer that was less than 10cm from the anal edge were studied and selected in the Hunan Cancer Hospital,and MRI was performed after they received concurrent radiochemotherapy(50Gy/25 times and oral administration of capecitabine 825mg/m2,twice a day).1 doctor from Department of Radiology and 1 doctor from Department of Radiotherapy independently delineated GTV under the sequences of T2WI,DWI and combination of both,respectively,the GTV on different images between the two observers was collected and analyzed,and the volume difference and outline delineated by the two observers were evaluated,so as to provide a scientific reference for further clinical and trial research.Results:The mean and standard deviation of T2GTV,DWIGTV and CombinGTV for the doctor from Department of Radiotherapy were 8.18±4.97,9.90±7.71 and 8.52±4.23(P>0.05),respectively;and the mean and standard deviation of T2GTV,DWIGTV and CombinGTV for the doctor from Department of Radiology were 3.10±4.91,4.49±5.64 and 3.52±3.61(P>0.05),respectively.The DICE indexes delineated by the two doctors under T2WI,DWI and T2WI/DWI modes were(0.33±0.49),(0.42±0.44)and(0.62±0.36),respectively.The GTV delineated by the doctor from Department of Radiotherapy was all obviously larger than that by the doctor from Department of Radiology.Under the three modes of T2WI,DWI and T2WI/DWI,ICC was 0.149(-0.089,0.576),0.234(-0.264,0.721)and 0.29(-0.139,0.738),respectively.Under the three modes of T2WI,DWI and T2WI/DWI,the average difference of GTV delineated by the two doctors was 5.079ml(95%CI:-8.519,18.68),5.412ml(95%CI:-10.36,21.18)and 4.994ml(95%CI:-2.651,12.639),respectively.Conclusion:Through studying the difference in observers delineating GTV under MRI image sequences after conventional radiotheraphy for rectal cancer,it is found that there is a big difference in delineating GTV between the doctors from Department of Radiology and from Department of Radiotherapy and also there is a poor agreement.When implementing late-course high-dose radiotherapy for rectal cancer,it is recommended that delineation of GTV should be performed and consensus agreed both by doctors from Department of Radiology and Radiation Oncology.