# 18F-FDG PET/CT for Risk Stratification and Prognosis of Patients with Hypermetabolic Gastrointestinal Stromal Tumors

## TL;DR

This study shows that 18F-FDG PET/CT can help predict outcomes and risk levels in patients with hypermetabolic gastrointestinal stromal tumors.

## Contribution

The study is the first to specifically investigate risk stratification and prognosis of hypermetabolic GISTs using PET/CT parameters.

## Key findings

- MTV is an independent PET parameter for predicting risk stratification in hypermetabolic GISTs.
- SUVmax is an effective predictor of both relapse-free and overall survival in these patients.
- Hypermetabolic GISTs are associated with higher risk and poorer prognosis compared to hypometabolic tumors.

## Abstract

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal neoplasm of the gastrointestinal tract. Currently, risk stratification of GISTs is based on the modified National Institutes of Health (NIH) criteria. 18F-FDG PET/CT is increasingly used for biological risk assessment, staging, and treatment response evaluation in GISTs. Studies show that hypometabolic GISTs generally have a lower risk stratification and better prognosis. Conversely, hypermetabolic GISTs carry high risk and are associated with a poorer prognosis, thus requiring more clinical attention. To our knowledge, no study has specifically investigated risk stratification and prognosis of hypermetabolic (SUVmax > 2.5) GISTs. These results suggest that PET parameters may assist in predicting risk stratification and prognosis in GIST patients.

Objectives: We aimed to evaluate the value of various PET parameters derived from 18F- FDG PET/CT for risk stratification and prognosis of hypermetabolic gastrointestinal stromal tumors (GISTs). Methods: This study included 43 patients who underwent 18F-FDG PET/CT imaging with hypermetabolic (SUVmax > 2.5) GIST and underwent surgical treatment. Clinicopathological characteristics, risk stratification, PET parameters including standard uptake values (SUVs), metabolic tumor volume (MTV), total lesion glycolysis (TLG), and heterogeneity index (HI), and follow-up data were reviewed. The relationship between PET parameters and risk stratification based on the modified National Institutes of Health (NIH) criteria was analyzed. PET parameters were assessed to predict relapse-free survival (RFS) and overall survival (OS), based on Cox regression analysis and Kaplan–Meier analysis. Results: The median follow-up duration was 50 months. During follow-up, 11 patients (25.58%) experienced recurrence and 8 (18.60%) died. In risk stratification, the high-risk group exhibited more frequent extragastric location, larger tumor size, higher mitotic count, and elevated PET parameters except SUVmax. MTV (≤32.68 vs. >32.68, 95% CI: 1.358–72.048, p = 0.024) emerged as an independent PET parameter of risk stratification. In univariate analysis, tumor location (gastric vs. extragastric), SUVmax (≤10.25 vs. >10.25), and HI (≤2.44 vs. >2.44) were significant prognostic factors for RFS. Tumor location and SUVmax were significant to OS on univariate analysis. However, in multivariate analysis, only SUVmax (95% CI: 1.549–46.071, p = 0.014) was an independent prognostic factor for both RFS and OS. Conclusions: 18F-FDG PET/CT demonstrates predictive value for hypermetabolic GIST patients. MTV derived from 18F-FDG PET/CT improves the ability of predicting risk stratification. SUVmax is an effective predictor of both RFS and OS.