Preoperative assessment of malignant potential of gastrointestinal stromal tumor by dual-time-point 18F-fluorodeoxyglucose positron emission tomography imaging: Usefulness of standardized uptake value and retention index
Yeongkeun Kwon1, Eunkyung Park2, Kisoo Pahk3, Sungeun Kim3, Min Ju Kim4, Daniel Graf5, Sungsoo Park6
1 Department of Family Medicine, Korea University College of Medicine, Seoul, Korea
2 Department of Diagnostic Radiology, PET Center, Yale University, New Haven, CT, Buffalo, NY, USA
3 Department of Nuclear Medicine, Korea University College of Medicine, Seoul, Korea
4 Department of Radiology, Korea University College of Medicine, Seoul, Korea
5 Department of Nuclear Medicine, The State University of New York at Buffalo, Buffalo, NY, USA
6 Department of Surgery, Division of Upper Gastrointestinal Surgery, Korea University College of Medicine, Seoul, Korea
Department of Surgery, Division of Upper Gastrointestinal Surgery, Korea University Anam Hospital, Korea University College of Medicine, Inchon-ro 73, Seongbuk-gu, Seoul 02841
Source of Support: None, Conflict of Interest: None
Background: To evaluate the usefulness of preoperative imaging with F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) for noninvasive risk assessment of gastrointestinal stromal tumor (GIST).
Materials and Methods: A retrospective review including 32 patients with pathologically proven GIST. Preoperative FDG-PET scan results including maximum standardized uptake values (SUVs) of the GISTs at 1 h postinjection (SUV1) were available for all tumors and SUVs at 2 h postinjection (SUV2) were available for 22 tumors. When both SUV1 and SUV2 were available, a retention index (RI, %) was calculated, and the correlation of these PET parameters with the histopathologic results was analyzed.
Results: SUV1 was significantly higher in tumors in the high-risk group (6.0 ± 2.7) compared to those in the low risk (3.0 ± 1.6) or very low-risk (2.7 ± 1.2) groups (P = 0.009 and 0.011, respectively). At a cutoff of 5.2, the SUV1 demonstrated sensitivity of 80% and a specificity of 89% for predicting high-risk GISTs. Tumor size was significantly correlated with SUV1 (r = 0.68, P < 0.001) and SUV2 (r = 0.66, P = 0.001), and SUV1, SUV2, and RI were significantly higher in tumors with mitotic index > 5/50 high-power field than in those with lower mitotic index. RI was significantly higher in tumors with C-kit mutation than in those with no C-kit mutation.
Conclusion: SUV1 measured during preoperative FDG-PET imaging correlated well with malignant potential of GISTs, especially for high-risk versus Low-/very-low-risk tumors. RI values correlated well with mitotic counts and C-kit mutation, suggesting that this mutation may have some influence on tumor metabolism.