Influence of Diabetes on the Interpretation of PET Scans in Patients With Esophageal Cancer.

PURPOSE: Patients with diabetes mellitus (DM) can have altered sugar transport into cells, potentially affecting the results of 18-FDG PET scans. The specific aim of this study was to determine the effect of DM on pre- and post-treatment standard uptake value (SUV) scores in patients undergoing chemoradiotherapy for esophageal cancer.

METHODS: Patients with locally advanced esophageal carcinoma undergoing preoperative or definitive chemoradiotherapy underwent pre- and posttreatment 18-FDG PET scans. Maximum SUV score was measured from the tumor before chemoradiotherapy and 3 to 4 weeks after chemoradiotherapy (preoperatively). Patients were identified as having DM by medical record review. Random serum glucose measurements were obtained prior to 18-FDG PET scans. The Wilcoxon signed-rank test was used to test for differences in SUV scores between patients with and without DM, and a generalized linear model with backward selection was applied to search for significant predictors of initial and posttreatment SUV scores.

RESULTS: Sixty-three patients underwent 18-FDG PET scans during the course of treatment for esophageal malignancies between 6/02 and 8/05. Fifty-four patients received chemotherapy. The median radiation dose was 46.8 Gy. Eighteen patients had DM, six were insulin-dependent DM (IDDM). There was no difference in initial SUV scores between DM and non-DM patients (P > .05). There was also no difference in initial SUV scores between IDDM and non-IDDM groups. Patients with tumors at the gastroesophageal junction had lower initial SUV scores compared to patients with tumors in the lower or mid-esophagus (P = .05). T stage was associated with initial SUV score (T2 lower than T3, P = .014). Older age (P = .03), diabetes (P = .007), higher T stage (P = .002), and presence of nodes (P = .05) were each positively associated with posttreatment SUV scores. Blood glucose levels prior to 18-FDG PET scan, endoscopic tumor length, and tumor location were not predictive of posttreatment SUV scores. Patients with DM had significantly lower posttreatment SUV scores compared to patients without DM (P = .04). Pathologic complete response or percent SUV decrease did not differ between patients with or without DM.

CONCLUSION: Regardless of glucose levels, DM and IDDM do not influence pretreatment SUV scores in patients with localized esophageal cancer. However, DM may influence posttreatment SUV scores and thus complicate interpretation of treatment response. Further confirmatory study in a larger cohort of DM patients to evaluate the relationship of posttreatment SUV score to pathologic response is warranted.