Different diagnostic criteria based on the SUVmax of primary tumors can improve the nodal staging in patients with breast cancer on FDG PET-CT

초록

Objectives Main object of our study was to determine how to improve the detectability in nodal metastasis of on FDG PET-CT in breast cancer. Methods We retrospectively reviewed 49 patients with breast cancer who underwent FDG PET-CT for initial staging work up. On FDG PET-CT, axillary lymph node (LN) was interpreted as positive, negative or indeterminate. The indeterminate LNs were characterized as hypermetabolic to background tissue but hypometabolic to mediastinal activity. On FDG PET-CT, the SUVmax of primary tumor (SUVtm and SIZEtm) were measured. We applied 3 different diagnostic criteria to assess the indeterminate LN state (Criteria I: Counting indeterminate as positive, Criteria II: Counting indeterminate as negative, Criteria III: Counting indeterminate LN as positive only when the SUVtm was less than 6). Accuracy, sensitivity, specificity, positive predictive value and negative predictive value were calculated under applying each criteria. Statistical significant of difference of 3 methods were determined by McNemar test. Results Of 49 patients, 16 had axillary LN metastasis. On FDG PET-CT, Axillary lymph nodes of 6, 30 and 13 patients were interpreted as positive, negative and indeterminate, respectivelyOf 13 indeterminate lymph node cases, 6 were positive (IP) and 7 were negative (IN) for metastasis. Significant difference in SUVtm between IN and IP (mean±SD, 11.6±2.4 vs 3.5±1.5, p<0.001) was found. When applying each diagnostic criteria, accuracy (Sensitivity, specificity, PPV, NPV) were 79.6% (37.5%,100%, 100%, 76.7%) for Criteria I, and 77.6% (75%, 78.8%, 63.2%, 86.7%) for Criteria II and 91.8% (75%, 100%, 100%, 89.2%) for Criteria III (p<0.05 by McNemar test). Conclusions On FDG PET CT, among the cases interpreted as indeterminate axillary LN, primary tumor metabolism of group with negative for lymph node metastasis was higher than that positive. Nodal staging using FDG PET-CT may be more accurate when we apply the diagnostic criteria based on metabolism of primary tumor in breast cancer.