ABSTRACT
Objective To compare the tumor sizes of primary lesions in pancreatic cancer based on CT scan and postoperative pathological analysis and measure the extent of filtration under a microscope,and to determine the CTV in radiotherapy target delineation.Methods A total of 19 patients with pancreatic cancer who were admitted to PLA General Hospital and Air Force General Hospital,PLA from 2013 to 2014 were analyzed.In 15 patients,the maximum diameters of tumor cross-section were measured based on the images of preoperative multi-slice spiral CT and postoperative gross samples,respectively.In 19 patients,the extent of tumor infiltration was measured on pathological sections under a microscope and the actual extent of infiltration was calculated.The paired t-test was applied to analyze the differences in the results of different measurement methods.Results In the 15 patients,the maximum tumor diameters measured with gross samples and CT scan were 33.6 mm and 30.1 mm,respectively (P=0.000),and the median and mean of the differences were 3.1 mm (1.2-8.0 mm) and 3.6±2.0 mm,respectively (95％ CI 1.2-6.0).In the 19 patients,the maximum actual infiltration distance and the maximum distance measured were 3.50 mm and 3.19 mm,respectively (P=0.000),and the median and mean of the differences were 0.31 mm (0.15-0.50 mm) and 0.30±0.09 mm,respectively.The maximum distance between the margin of primary lesions and the infiltrating lesions was 5.21 mm,with a median of 3.34 mm (2.19-5.21 mm) and a mean of 3.50± 0.88 mm (95％ CI 2.19-5.06).Conclusions Contrast-enhanced CT scan underestimates the actual size of primary lesions in pancreatic cancer,and an extension of 5 mm outside gross tumor volume (GTV) as CTV may not be sufficient.It is recommended to extend another 1-3 mm outside GTV as CTV.