Abstract
OBJECTIVE: To investigate the value of Fluorine-18 fluorodeoxyglucose-positron emission tomography/computed tomography ([(18)F]-FDG PET/CT) in the diagnostic of patients having gastrointestinal (GI) cancers with second primary malignancies (SPMs). METHODS: Fifty-seven patients (57/1384, 4.1%) diagnosed with SPMs were retrospectively enrolled. The analysis included the following factors: clinical information (sex, age, smoking and drinking history, BMI), site of the second primary tumor, the interval between the diagnoses of the first GI cancer and the SPMs, and histopathology. According to the incidence of SPMs, the patients were divided into lung cancer and non-lung cancer groups. The two groups were compared smoking and drinking history, interval time, distant metastasis, and [(18)F]-FDG PET/CT-related parameters (maximum standardized uptake value [SUV(max)], metabolic tumor volume [MTV], and total lesion glycolysis [TLG]). Twenty-two patients with synchronous cancers were included to compare the Ki-67 index and [(18)F]-FDG PET/CT-related parameters (SUV(max), MTV, and TLG) between the first and second primary tumors. RESULTS: The most common SPMs of the GI system was lung cancer (47.4%, 27/57). Genetic testing revealed abnormalities in three patients, and the pathological type was adenocarcinoma in all three cases. Among the 57 patients diagnosed with multiple cancers (27 synchronous, 30 metachronous), the lung was the most frequent site for both synchronous and metachronous tumors. Between the lung cancer group and the non-lung cancer group differences in the interval between the first GI, age, distant metastasis rate, SUV(max), MTV, and TLG were not statistically significant (P = 0.09, P = 0.288 and P = 0.57). Chest CT and PET/CT were performed preoperatively in all 27 patients in the lung cancer group, and the diagnostic accuracy of PET/CT for the second primary tumor in the group was 100% and chest CT diagnostic accuracy was 77.8%. We found significant differences in the Ki-67 indices between the synchronous cancers (64.5 ± 24.0 vs. 35.1 ± 22.7, p < 0.000). Furthermore, the Ki-67 index was highly expressed in patients with lymph node and distant metastases, but the SUV(max), MTV, and TLG were not significantly different between the groups with lymph node and distant metastases (P = 0.366, P = 0.565 and P = 0.869). CONCLUSION: The most common SPMs of the GI system was lung cancer. We found that [(18)F]-FDG PET/CT in patients with GI cancers can help identify primary and metastatic lesions and detect the presence of SPMs at an early stage. Patients with SPMs may have unique characteristics, can be beneficial in helping high-risk patients with early intervention.