RESUMEN
BACKGROUND: Matrix metalloproteinase-9 (MMP-9) is an important mediator of invasion and metastasis in neoplasia. In thyroid cancer expression levels correlate with aggressiveness but data on peripheral MMP-9 levels are less definitive. OBJECTIVE: Prospective study evaluating serum MMP-9 in the diagnosis and prognosis of papillary thyroid cancer. METHODS: Serum samples of MMP-9 were drawn before surgery in 185 consecutively enrolled patients with nodular thyroid disease, stratified on pathology as benign disease (N= 88) and papillary thyroid cancer (N= 97). Serum MMP-9 was measured by an immunometric assay. RESULTS: MMP-9 levels were not different between benign vs malignant pathology (p= 0.3). In papillary thyroid cancer there was no significant difference in MMP-9 levels between histologies, TNM stage and invasive/non-invasive cancers. High-risk patients with multiple features of aggressiveness had significantly higher MMP-9 levels compared to low-intermediate risk patients (767.5 ± 269.2 ng/ml vs 563.7 ± 228.4 ng/ml, p= 0.019). A cut-off of 806 ng/ml distinguished high from low-intermediate risk patients with a sensitivity of 60% and a specificity of 87.36%, p= 0.018. In patients with available follow-up data (N= 78), MMP-9 was higher in patients who required ⩾ 2 doses of 131I therapy (p= 0.009) and in those with biochemical evidence of persistent disease/who required additional therapy to achieve disease-free status (p= 0.017). CONCLUSION: Serum MMP-9 is not useful in the diagnosis of PTC, but preliminary data shows that high pre-surgical serum MMP-9 levels may identify patients at higher risk of persistent disease who require intensive treatment. Large volume prospective studies are required to confirm this observation.