Diagnostic and Prognostic Value of F18 FDG PET/CT in Assessing Nodal Metastasis in High-Risk GIST Patients

Document Type : Original Article

Authors

1 Nuclear Medicine and radiotherapy department, national cancer institute, Cairo University

2 nuclear Medicine and Radiotherapy departement, national cancer Institute, Cairo University

3 Professor of Nuclear Medicine, Faculty of Medicine, Cairo University.

4 Nuclear medicine department , national cancer institute , Cairo university , Egypt

Abstract

Aim: In order to diagnose nodal metastases and assess the prognosis and response to imatinib mesylate (Gleevec), this study set out to determine the diagnostic and prognostic utility of F18 FDG PET/CT.
Materials and Procedures: FDG PET/CT scans were retrospectively evaluated in 159 individuals with pathologically confirmed GIST (77 females, 82 males, mean age: 49.2±12.7). A total of 194 PET/CT tests (57 pre-treatment and 137 follow-up) were performed to analyze nodal lesions throughout imatinib therapy. The criteria of reference were pathological and clinical/radiological follow-up for a period of 13-15 months.
Findings The mean age of the 29 patients (18.2%) with lymph node (LN) metastases was 53.2±12.7. Sixty-two percent of the patients had primary stomach disease, and sixty-nine percent had high-risk spindle cell disease. The size ranged from 1 to 8.7 cm, with a mean SUVmax value of 6.7 ± 4.5 and a size of 2.1 cm. Only six patients had isolated nodal metastases, while the other twenty-three patients had multiple and triple sites of metastases (liver and/or peritoneal deposits). There are 89 lymph nodes seen in all, including 17 with mediastinal deposits and 70 with abdomino-pelvic deposits. Compared to 55% of metastatic patients without nodal involvement and only 6.5% of non-metastasized patients, 21 patients (72.4%) in the group with nodal metastases suffer disease progression. (P value <0.001). The mortality rate was not statistically significant, with four of the 29 patients with nodal metastases (13.7%) dying, compared to around 10% and 4.9% for the other metastatic and non-metastasized groups, respectively. (p value ~0.841)
In conclusion: With an incidence of 18.2%, lymph node metastases are thought to be a poor prognostic factor for GIST patients, FDG PET/CT appears to be an effective method for detecting lymph nodes and evaluating imatinib therapy response.

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