Malignant diagnosis and prognostic analysis of 89 GIST patients using preoperative FDG-PET

There is no preoperative imaging accurately diagnose malignancy of gastrointestinal stromal tumor (GIST). To evaluate the usefulness of preoperative [¹⁸F]2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) in the malignant diagnosis and prognostic analysis of GIST. Eighty-nine consecutive patients with GIST who underwent curative surgery were reviewed retrospectively. PET scan was performed within 2-3 weeks before surgery and maximum standardized uptake values (SUVmax) were assessed for GIST. The relationship between prognostic factors and prognosis of GIST and SUVmax were evaluated. Tumor size, mitotic count, and Ki-67 index showed significant positive correlations with the SUVmax. When the cutoff value was set as SUVmax 5.68, the accuracy was 86.5% for the high-risk group, 76.4% for the recurrence group, and 73.0% for the death group. The group with SUVmax ≥ 5.68 demonstrated a significantly lower 10-year relapse-free survival than the group with SUVmax < 5.68 (55.2% vs. 98.2%, P < 0.001), while the group with SUVmax ≥ 5.68 demonstrated a significantly lower 10-year overall survival than the group with SUVmax < 5.68 (68.0% vs. 97.6%, P < 0.001). In GISTs, FDG-PET is a very useful imaging marker for the diagnosis of malignant GISTs, such as those in high-risk and poor-prognosis groups.