Multi-center and multi-reader comparison of abdominopelvic non-contrast and contrast-enhanced CT in the postoperative surveillance of gastrointestinal stromal tumors.

Background: Due to the significant risk of recurrence, postoperative surveillance of gastrointestinal stromal tumors (GISTs) is crucial. Contrast-enhanced computed tomography (CECT) is the standard imaging modality; however, repeated long-term examinations result in cumulative contrast and radiation exposure. Non-contrast computed tomography (NCCT) offers a safer alternative; however, high-quality multi-center evidence comparing its diagnostic performance with that of CECT remains limited. This study aimed to compare the diagnostic performance of abdominopelvic NCCT and CECT for detecting postoperative recurrence or metastasis in patients with GISTs. Methods: This retrospective multi-reader, multi-case (MRMC) study was conducted using data from patients with GISTs who underwent radical resection between September 2011 and January 2023. Five radiologists (with 5-20 years of experience) blindly and independently reviewed NCCT and CECT datasets. Diagnostic accuracy was analyzed using R and Python, with subgroup analyses based on National Institutes of Health (NIH) risk stratification and lesion location. A P value <0.05 was considered statistically significant. Results: Both NCCT and CECT demonstrated good diagnostic accuracy across both institutions [West China Hospital, Sichuan University (Institution I): area under the curve (AUC) 0.863 Conclusions: This multi-center MRMC study demonstrates that NCCT is a valuable alternative to CECT for postoperative GIST surveillance, particularly in patients requiring long-term follow-up or those with contraindications to contrast. NCCT has high specificity comparable to that of CECT, while mitigating the risks of cumulative contrast and radiation exposure; however, expert interpretation remains important for detecting small lesions due to its lower sensitivity.