3448 - Exploratory Analysis of Lymph Node Ratio and Iodine-Avid Disease Extent After Radioactive Iodine Treatment in Differentiated Thyroid Cancer
Presenter(s)
S. I. Cortes-Iriarte1, N. Ud Din2, S. Yarlagadda2, S. C. George2, A. McGoron3, R. P. Tolakanahalli2, and N. S. Kalman2,4; 1Florida International University, Herbert Wertheim College of Medicine, Miami, FL, 2Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, FL, 3Department of Biomedical Engineering, Florida International University, Miami, FL, 4Department of Oncological Sciences, Florida International University, Herbert Wertheim College of Medicine, Miami, FL
Purpose/Objective(s): Multiple clinicopathologic factors have been proposed to predict recurrence risk in differentiated thyroid cancer. Lymph node ratio (LNR), defined as the proportion of involved lymph nodes among those sampled, has been proposed as a marker of tumor burden in differentiated thyroid cancer (DTC). However, its relationship with the extent of iodine-avid disease on whole body scans (WBS) after radioactive iodine (RAI) treatment remains unclear, and LNR does not affect risk stratification in ATA guidelines for DTC treatment. We performed an exploratory analysis to evaluate the relationship between LNR and patterns of RAI uptake on WBS in a retrospective DTC cohort.
Materials/Methods: We retrospectively reviewed 20 patients with DTC treated with radical surgery followed by adjuvant RAI therapy at a single institution. Post-RAI scans were categorized as demonstrating remnant-only uptake versus structural iodine-avid disease (central neck, lateral neck, or distant uptake). LNR was analyzed as a continuous variable and dichotomized at =0.3. Associations between LNR and WBS uptake patterns were assessed using Mann-Whitney U and Fisher’s exact tests.
Results: Structural iodine-avid disease was observed in 8 of 20 patients (40%). Patients with structural uptake demonstrated higher mean LNR compared with those with remnant-only uptake (0.34 vs 0.26); however, this difference did not reach statistical significance (p = 0.79). Dichotomized analysis likewise showed no significant association between high LNR (=0.3) and structural uptake (50% vs 40%, OR 1.5, Fisher’s exact p=1.0).
Conclusion: LNR demonstrated a trend towards increased risk of structural disease uptake on WBS, although no statistically significant association was detected in this pilot cohort. The observed directional trend is biologically plausible, as greater nodal tumor burden may correlate with more extensive residual iodine-avid disease. Larger, adequately powered studies are warranted to determine whether LNR may serve as an independent risk factor for residual disease presence and for postoperative risk stratification.