방사선의학 웹진

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Abstract

Background: 

A change in tumor size is well-validated and commonly used value for evaluating response to chemotherapy in cancer. Metabolic changes induced by chemotherapy are related to prognosis in several tumor types. However, the clinical implication of metabolic changes in patients with advanced gastric cancer (AGC) undergoing chemotherapy remains unclear. We aimed to evaluate response of tumor size and metabolism in AGC during chemotherapy and to reveal the relationship between them in view of their impact on patient survival. 

Methods: 

We prospectively enrolled patients with AGC before the initiation of first-line palliative chemotherapy. Using baseline and follow-up contrast-enhanced computed tomography (CT) and 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET), we assessed the tumor diameter, maximum standardized uptake value (SUVmax), and total lesion glycolysis (TLG) in each lesion, and their changes during chemotherapy at the same time. We included all lesions with the maximal longest diameters over 1 cm on CT, and each lesion was evaluated by matched 18F-FDG PET. We analyzed the association between changes in tumor metabolism and tumor size, and performed outcome analysis on overall survival (OS) and progression-free survival (PFS). 

Results: 

Seventy-four patients were enrolled, and the number of all lesions included in this study was 620. Compared to adenocarcinomas, poorly cohesive carcinomas demonstrated lower SUVmax irrespective of tumor size (p<0.001). Human epidermal growth factor receptor 2 (HER2)-positive tumors showed higher SUVmax than HER2-negative tumors (P = 0.002). Changes in SUVmax due to chemotherapy had a linear correlation with changes in tumor size of each lesion, and a 30% tumor size reduction was associated with a 50% SUVmax reduction (p<0.001). TLG changes also correlated with tumor size changes (p<0.001). Better OS and PFS were obtained in patients with both tumor size and SUVmax reduction than in patients with either size or SUVmax reduction only (OS, P = 0.003; PFS, P = 0.038). 

Conclusion: 

Changes in tumor metabolism induced by chemotherapy correlated with changes in tumor size in AGC. Considering both changes in metabolism and size could help predict a more accurate prognosis for AGC patients undergoing chemotherapy.

Author information​

Park S1, Ha S2, Kwon HW2, Kim WH2, Kim TY1, Oh DY1, Cheon GJ2, Bang YJ1.

1 Department of Internal Medicine, Seoul National University Hospital, Republic of Korea

2 Department of Nuclear Medicine, Seoul National University Hospital, Republic of Korea