Endocrine Abstracts

Background: Medullary thyroid cancer (MTC) is a rare malignancy with a variable and sometimes unpredictable disease course. To predict the course of disease more accurately at diagnosis, we introduce dynamic risk stratification by analyzing factors related to “stage migration” within the first 5 years after diagnosis.

Methods: All patients diagnosed at the University Medical Center of Groningen between 1999 and 2015 were retrospectively studied. Patients were staged according to the 8^th edition of the TNM classification and variables were collected. Stage migration was defined as 1) an upgrade of the N and/or M stage, i.e., the development of i) a lymph node metastasis in a previously unaffected cervical compartment or ii) distant metastasi/es in an initially M0 staged patient or 2) death due to MTC progression, within 5 years after diagnosis. Clinical and pathological variables were then evaluated in univariate Cox regressions to find prognostic factors.

Results: Of the 75 included patients, 41 were male and 47 had sporadic MTC. The median age at diagnosis was 49 (IQR 32 – 58) years. A total of 29 (39%), 7 (9%), 9 (12%) and 30 (40%) of the patients were classified with stage I, II, III and IV, respectively. Sporadic MTC patients had a higher stage at diagnosis than hereditary patients (P < 0.001). Five years after diagnosis, 61 (81%) patients were still alive. Eleven patients died due to MTC progression and 3 died from other causes. Twenty-one out of 75 included patients developed stage migration within 5 years after diagnosis, after a median time of 17.0 (IQR 11.5 – 30.5) months. Stage migration was a result of an upgrade of the N and/or M stage in 10 patients, disease-specific death in 8 patients and a result of both (upgrade of N and/or M stage followed by death) in 3 patients. Stage migration occurred in 1 (14%), 6 (67%) and 14 (47%) of stage II, III and IV patient(s), respectively. In univariate Cox regressions, sporadic MTC, palpable lymph node(s) at diagnosis, a higher TNM stage, angioinvasion, a positive resection margin, and extrathyroidal growth significantly increased the risk of stage migration.

Conclusion: MTC is a dynamic disease where disease progression is always lurking. This stage migration model could improve the clinician’s prediction of disease progression and thereby help to design a better patient-tailored follow-up strategy after initial treatment. To verify this method, further collaborative studies with larger datasets need to be performed.