# Combined Ultrasound and MRI Assessment in Patients Undergoing Reoperation for Recurrent Papillary Thyroid Carcinoma: Oncological Outcomes and Surgical Safety

## TL;DR

Combining ultrasound and MRI improves detection of cancer spread in thyroid cancer reoperations, leading to better surgical outcomes without increased risk.

## Contribution

The study demonstrates that combining ultrasound with MRI improves lymph node detection and surgical outcomes in high-risk thyroid cancer reoperations.

## Key findings

- Combined ultrasound and MRI increased sensitivity for detecting central lymph node metastasis from 52.5% to 90.9%.
- The combined approach led to higher rates of central neck dissections and better biochemical responses in reoperated patients.
- Improved recurrence-free survival was observed in patients with ≥2 positive central nodes in the combined group.

## Abstract

Papillary thyroid cancer is the most common type of thyroid cancer, and it is sometimes recurrent after initial treatment, requiring reoperation. Ultrasound is typically used to assess whether cancer has spread to nearby lymph nodes before operations, but it may miss some cancerous lymph nodes when not paired with another form of assessment. This study explored whether supplementing ultrasound with magnetic resonance imaging could improve surgical planning and outcomes in patients undergoing reoperation. The results showed that the combined assessment significantly helped in detecting more involved lymph nodes, leading to more accurate surgical targeting and improved treatment response, without increasing complication rates. These findings suggest that while MRI is not needed for all patients, it may provide added value in selected high-risk cases, helping surgeons perform safer and more effective reoperations.

Reoperation for papillary thyroid carcinoma (PTC) requires precise lymph node metastasis assessment, yet ultrasound (US) alone may be insufficient in complex or high-risk cases. This study evaluated whether supplementing US with magnetic resonance imaging (MRI) improves surgical guidance and outcomes in reoperation. We retrospectively analyzed 375 patients who underwent reoperation between 2014 and 2022. Propensity score matching yielded 101 patients in the USUS-only group and 62 in the US+MRI group. Pathological and imaging data were compared to assess diagnostic performance, surgical outcomes, biochemical responses, and recurrence-free survival. The combined approach significantly increased sensitivity for detecting central lymph node metastasis from 52.5% to 90.9% and resulted in higher rates of central neck dissections (65.1% versus 45.5%) with greater lymph node yield (median: 29 versus 20) but lower lymph node ratios. More patients in the combined group achieved excellent biochemical responses (50.0% versus 27.7%). While overall recurrence-free survival (RFS) was not significantly different, the US+MRI group showed improved RFS among patients with ≥2 positive central nodes (HR = 0.24, p = 0.032). Importantly, complication rates were comparable, suggesting that improved outcomes were achieved without added surgical risk. Combined US and MRI assessment enhances diagnostic performance and may improve surgical and oncological outcomes in select high-risk patients undergoing PTC reoperation.