# Occurrence of Metastases in Differentiated Thyroid Carcinoma Patients: A Retrospective Study in Morrocco Covering 10 Years of Follow-Up

## TL;DR

This study identifies risk factors for distant metastases in thyroid cancer patients in Morocco, helping to guide treatment and monitoring strategies.

## Contribution

The study provides a 10-year follow-up analysis of metastasis risk factors specific to Moroccan DTC patients.

## Key findings

- 6.2% of DTC patients developed distant metastases during the 10-year follow-up.
- Lung and bone were the most common metastasis sites, occurring in 46.0% and 38.0% of cases, respectively.
- Age ≥ 55, male gender, and other clinical factors were significantly associated with metastasis occurrence.

## Abstract

Introduction: Distant metastases in differentiated thyroid carcinoma (DTC) are uncommon but significantly impact patient outcomes. The disease-specific mortality rates are notably higher among patients with metastases, reflecting the aggressive nature of this condition. This study aimed to identify predictive factors for the occurrence of distant metastases in Moroccan patients treated for DTC.

Material and methods: This was a retrospective cohort study that included patients diagnosed with DTC between 2004 and 2012 and followed up at the nuclear medicine department of Ibn Rochd Hospital, Casablanca, Morocco. All patients diagnosed with DTC who did not have metastasis at the diagnosis were included with a mean follow-up time of 10.4 years. The Kaplan-Meier method was used to study the occurrence of metastases at 10 years. The diagnosis of metastases was confirmed by iodine scintigraphy and fludeoxyglucose F18 (18F-FDG) PET/CT.

Results: A total of 1,357 patients were included in the study. Women represented 89.5% of the study population. The mean age was 44, with a range of 14-85 years. The most frequent histological type was papillary thyroid cancer, accounting for 93.5% of cases. During follow-up, 6.2% of patients developed metastases. The mean time from diagnosis to metastasis was 4.27 years. Lung (46.0%) and bone (38.0%) were the most common sites of distant metastases.

The study of factors predictive of the occurrence of metastases showed that age ≥ 55 years, male gender, follicular histological type, extra-thyroidal extension, vascular invasion, tumor size > 4 cm, detectable thyroglobulin level, disease stages (≥II), high risk of relapse, and the presence of cardiovascular comorbidities were associated with the occurrence of metastases.

Conclusion: The identification of factors predictive of the occurrence of metastases offers a valuable opportunity to stratify patients according to their level of risk. This stratification makes it possible to optimize management through an adapted and more aggressive therapeutic approach for high-risk patients while ensuring close monitoring, particularly during the first five years following diagnosis.