Postoperative FDG-PET/CT staging in GIST: Is there a benefit following R0 resection?

AimResection of the primary tumor with intraoperative staging is the standard procedure in patients with gastrointestinal stromal tumors (GIST). FDG-PET/CT has shown high accuracy when assessing treatment response in GIST patients. This study was designed to assess the accuracy of postoperative FDG-PET/CT to stage for occult tumor seeding in patients with R0 resection and without intraoperative detection of metastases.Patients and methods48 consecutive patients (mean age: 59 y) with histologically proven GIST underwent whole-body FDG-PET/CT after R0-resection without intraoperative detection of metastases. Fused data sets were assessed for metastases by a nuclear medicine physician and a radiologist. Histology of potential lesions and a clinical/radiological follow-up with a mean of 614 ± 415 d served as standards of reference.ResultsFDG-PET/CT detected occult peritoneal metastases in 2 patients (4%). In 6 patients (13%) who later developed metastases postoperative FDG-PET/CT was falsely negative. False-positive findings were detected in 5 cases (10%) caused by increased FDG-uptake due to tissue regeneration postoperatively. In 3 patients (6%) other, formerly unknown malignancies were detected. The sensitivity and specificity of FDG-PET/CT for the detection of intraoperatively occult GIST metastases were 25% and 88%, respectively.ConclusionFDG-PET/CT performed immediately after R0-resection of GIST without intraoperative detection of metastases does not seem to be a sufficient tool to detect clinically occult metastases.