# An Assessment of the Effectiveness of Preoperative İmaging Modalities (MRI, CT, and 18F-FDG PET/CT) in Determining the Extent of Disease Spread in Epithelial Ovarian–Tubal–Peritoneal Cancer (EOC)

## TL;DR

This study compares MRI, CT, and PET/CT in detecting the spread of epithelial ovarian cancer, finding that all are effective for larger tumors but struggle with smaller ones.

## Contribution

The study evaluates the diagnostic accuracy of three imaging modalities for EOC, highlighting their limitations in detecting small miliary implants.

## Key findings

- MRI, CT, and PET/CT showed high sensitivity for tumors ≥ 0.5 cm but low sensitivity for smaller implants.
- All three modalities had excellent AUCs for ≥ 0.5 cm tumors, with MRI performing slightly better.
- Combining PET/CT with MRI or CT may reduce false negatives for miliary disease.

## Abstract

Background and Objectives: Epithelial ovarian–tubal–peritoneal cancer (EOC) is the most common type of ovarian cancer. Optimal cytoreductive surgery is the most important prognostic factor in its management. When complete cytoreduction is anticipated to be challenging, neoadjuvant systemic chemotherapy (NACT) becomes an alternative. Imaging modalities are utilized in the decision-making process for primary treatment. The purpose of this study is to evaluate the diagnostic performance and accuracy of preoperative MRI, CT, and 18F-FDG PET/CT in detecting the extent of EOC. Materials and Methods: Between 2017 and 2018, 24 patients with primary (with or without neoadjuvant chemotherapy) or recurrent EOC diagnosed at the Department of Gynecologic Oncology, Istanbul University, Istanbul Faculty of Medicine, were enrolled in this study. These 24 women underwent preoperative imaging modalities within 7 days prior to surgery. The results were compared with histopathological findings, considered the gold standard. Results: We evaluated 24 anatomic regions most commonly involved in EOC. The sensitivity of MRI, CT, and PET/CT in detecting ≥ 0.5 cm implants was 95%, 84%, and 86%, respectively. However, when including implants < 0.5 cm, sensitivity decreased significantly to 40%, 38%, and 42%, respectively. The calculated area under the curve (AUC) for tumors, including those < 0.5 cm, was evaluated as weak for all three modalities (MRI: 0.689, CT: 0.678, PET/CT: 0.691), with PET/CT detecting the largest area. For detecting tumors ≥ 0.5 cm, the AUCs were 0.974, 0.921, and 0.923 for MRI, CT, and PET/CT, respectively. The largest AUC was calculated with MRI, and the AUCs for all three methods were evaluated as excellent. Accuracy was comparable among all three imaging modalities, and no statistically significant differences were found (p < 0.05). Conclusions: While imaging modalities are valuable tools for evaluating abdominal spread in epithelial ovarian cancer (EOC), they have demonstrated limited success in detecting miliary disease. The risk of false negatives for miliary tumors on PET/CT may be mitigated by combining it with other imaging modalities such as MRI or CT. Further investigations are necessary to identify more accurate imaging techniques for this challenging clinical scenario.