The relationship between microscopic tumor size and CT tumor size in pancreatic ductal adenocarcinoma.

OBJECTIVES

To investigate the exact relationship between CT tumor size and the microscopic tumor size in PDAC.

MATERIALS AND METHODS

We enrolled 310 patients with pathologically confirmed PDAC without preoperative adjuvant therapies who underwent CT examination from June 2016 and December 2018. Smooth curve fitting and a segmented regression model were used to analyze the threshold effect between CT tumor size and the microscopic tumor size.

RESULTS

The tumor size was 2.93±1.15 cm under the microscope and 3.00±1.23 cm in CT. The mean bias was 0.067 cm between CT and microscopic assessments. The accuracy of CT T stages was 61.02% (36/59), 79.41% (162/204) and 57.45% (27/47) in T1, T2 and T3, respectively. A non-linear relationship was detected between CT tumor size and the microscopic tumor size, with a turning point of 4.3 cm. On the left of the inflection point, the effect size, 95% confidence interval, and p value were 0.51, 0.40 to 0.63, and <0.0001, respectively. However, we observed no relationship between CT size and microscopic tumor size on the right of the inflection point (0.22, 0 to 0.44, 0.053).

CONCLUSIONS

The relationship between CT and the microscopic tumor size is non-linear. When the CT tumor size was <4.3 cm, every 1-cm increase in CT tumor size was associated with a 0.56 cm increase in microscopic tumor size. When the CT tumor size was >4.3 cm, every 1-cm increase in CT tumor size was associated with a 0.91 cm increase in microscopic tumor size.