Usefulness of CT volumetry for primary gastric lesions in predicting pathologic response to neoadjuvant chemotherapy in advanced gastric cancer.

BACKGROUND: To investigate the utility of CT volumetry for primary gastric lesions in the prediction of pathologic response to neoadjuvant chemotherapy in patients with resectable advanced gastric cancer (AGC).

MATERIALS AND METHODS: Thirty-three consecutive patients with resectable AGC stage >or=T2 and N1), who had been treated with neoadjuvant chemotherapy and radical gastric resection, were prospectively enrolled in this study. There were 30 men and 3 women with a mean age of 53.8 years. Contrast-enhanced CT was obtained after gastric distention with air before and after chemotherapy using a MDCT scanner. Pre- and post-chemotherapy thickness or short diameter and volume of the primary gastric tumor and largest lymph node (LN), were measured using a dedicated 3D software by two radiologists in consensus. PET/CT was also performed and the peak standardized uptake value (SUV) of primary gastric tumor and largest LN before and after chemotherapy was measured. The percentage diameter, volume, and SUV reduction rates for both the primary gastric tumor and the LN, were calculated and correlated with the histopathologic grades of regression using the Spearman correlation test. Differentiation between pathologic responders and nonresponders was assessed using receiver operating characteristic (ROC) analysis.

RESULTS: Among the three CT parameters which showed significant correlation with the histopathologic grades of regression, the correlation factor was highest in the percentage volume reduction rate of primary gastric tumor (rho = 0.484, P = 0.004) followed by percentage volume reduction of the index node (rho = 0.397, P = 0.022), and percentage diameter reduction of the index node (rho = 0.359, P = 0.04). However, the percentage thickness decrease rate (P = 0.208) and the percentage SUV reduction rate (P = 0.619) of primary gastric tumor were not significantly correlated with the histopathologic grades of regression. When the optimal cutoff value of the percentage volume reduction rate of primary gastric tumor was determined to be 35.6%, a sensitivity of 100% (16/16) and a specificity of 58.8% (10/17) were achieved.

CONCLUSION: CT volumetry for primary gastric tumor may be the most accurate tool in the prediction of pathologic response following neoadjuvant chemotherapy in patients with resectable AGC.