OP15 – Microscopic positive margins strongly predict reduced disease-free survival in T4a papillary thyroid cancer

      Abraham, Earl1; Roshan, David2; Tran, Bryan1; Graham, Susannah1; Lehane, Christopher1; Wykes, James1; Campbell, Peter1; Ebrahimi, Ardalan1 1 Head and Neck Unit, Department of Surgery, Liverpool Hospital, Sydney, Australia 2 South Western Sydney Clinical School, UNSW, Sydney, Australia Background/Purpose: Although microscopic positive margins (MPM) appear to have no independent prognostic impact in papillary thyroid cancer (PTC),1-3 it is unclear whether this applies to patients with macroscopic extrathyroidal extention (ETE) involving the subcutaneous soft tissues, trachea, larynx, oesophagus and/or recurrent laryngeal nerve (T4a disease). A trend towards reduced local control has been reported in T4a tumors with MPM.4 Objectives: To determine if MPM impact disease-free survival (DFS) in patients with T4a PTC. Methods: A retrospective analysis of 610 patients with PTC identified 39 patients with T4a disease and median follow-up of 3.3 years. Univariate Cox regression was used to evaluate the association between MPM and DFS. Results: MPM were rare in the absence of ETE (5.4%) and strongly associated with microscopic and macroscopic ETE (32.1% and 32.6%, respectively; p<0.001). On univariate analysis, MPM were not associated with DFS in patients with no ETE (HR 1.7; p=0.315), microscopic ETE (HR 1.6; p=0.365) or macroscopic ETE limited to the strap muscles (HR 1.2; p=0.867). In contrast, MPM were associated with significantly reduced DFS in T4a disease (HR 4.1; p=0.041). The result was robust to adjustment for radioactive iodine administration (HR 4.1; p=0.040). A full multivariable analysis could not be performed due to the limited number of events and study size. Discussion & Conclusion: Whilst MPM do not appear to influence DFS in the majority of patients with PTC, they are associated with a 310% increased risk of recurrence in T4a disease. These findings need to be validated in larger multi-institutional studies. References: 1. Wang, L. Y., Ghossein, R., Palmer, F. L., Nixon, I. J., Tuttle, R. M., Shaha, A. R., et al. (2015). Microscopic Positive Margins in Differentiated Thyroid Cancer Is Not an Independent Predictor of Local Failure. Thyroid, 25(9), 993–998. 2. Kluijfhout W.P., Paternak J.D., Kwon J.S., Lim J., Shen W.T., Gosnell J.E., Khanafshar E., Duh Q.Y., Suh I. (2016). Microscopic Positive Tumor Margin Does Not Increase the Risk of Recurrence in Patients with T1-2 Well-Differentiated Thyroid Cancer. Annals of Surgical Oncology. 23(5):1446-51, 2016 May.    3. Suh, Y. J., Kwon, H., Kim, S.-J., Choi, J. Y., Lee, K. E., Park, Y. J., et al. (2015). Factors Affecting the Locoregional Recurrence of Conventional Papillary Thyroid Carcinoma After Surgery: A Retrospective Analysis of 3381 Patients. Annals of Surgical Oncology, 22(11), 3543–3549. 4. Hartl, D. M., Zago, S., Leboulleux, S., Mirghani, H., Déandreis, D., Baudin, E., & Schlumberger, M. (2013). Resection margins and prognosis in locally invasive thyroid cancer. Head & Neck, 36(7), 1034–1038.


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