Introduction: differentiated thyroid cancer (DTC) is the most frequent endocrine tumor generally showing a favourable outcome. The American Thyroid Association (ATA) classification system is not only useful to assess the risk of recurrence but also guides tumor follow-up. However, this system shows a static image of the patient at the beginning of treatment based on clinical and pathological features, and it has not been designed to be modified along the clinical course of disease. Therefore, the Memorial Sloan-Kettering Cancer Center (MS-KCC) has designed a reclassification system after 2 years of the initial treatment (IT) thus providing a dynamic perspective of each patient.
Objective: to report our experience with the MS-KCC risk of recurrence reclassification system on DTC patients.
Materials and methods: retrospective observational descriptive study of the results of the reclassification system of the DCT patients after two years of IT with surgery and radioiodine ablation, between October 2004 and April 2011. Data was obtained by reviewing the charts of patients. All surgeries, laboratory determinations and nuclear medicine procedures took place at our Hospital. Patients were classified according to initial risk of recurrence based on the ATA system and they were reclassified following the system proposed by the MS-KCC 2 years after IT. Patients with antithyroglobulin antibodies > 12 IU/ml were excluded due to interference with thyroglobulin determination.
Results: we reviewed data of 31 patients diagnosed with DTC. They were classified according to the ATA system as: low risk 17 (54.8 %), intermediate risk 13 (42 %) and high risk 1 (3.2 %) and they were reclassified following the MS-KCC system as having: excellent response 25 (80.6 %), acceptable response 6 (19.4 %) and incomplete response 0 (0 %). An excellent response was observed in 14 (82.4 %) and an acceptable response was observed in 3 (17.6 %) of the low-risk classified patients; an excellent response was observed in 11 (84.6 %) and an acceptable response was observed in 2 (15.4 %) of the intermediate-risk classified patients and in the high-risk group 1 patient (100 %) presented an acceptable response. Clinical status of patients after 2 years of IT: 25 (80.6 %) with no evidence of disease (NED), 6 (19.4 %) with biochemical persistence (BP) and 0 (0 %) with structural persistence (EP), recurrence (R) or death (D). After a mean long-term follow-up period of 51.3 months, the clinical status was: 25 (80.6 %) with NED, 4 (12.9 %) with BP and (0 %) with EP, R or D; for the remaining 2 (6.5 %) no long-term follow-up data was available (ND). At the end of the long-term follow-up period, 24 (96 %) patients with excellent response after 2 years of IT remained NED, whereas 1 (4 %) was reported as ND and 1 (16.7 %) patient with acceptable response after 2 years of IT remained NED (initially this was a low-risk patient), 4 (66.6 %) remained BP, 1 (16.7 %) was reported as ND and no EP, R or D was observed.
Conclusions: 1) reclassification of patients was particularly useful in the intermediate risk group because 84.6 % of these patients had an excellent response after two years of IT, 2) reclassification of patients based on the response to IT, allows us to optimize their follow-up and 3) although the mean long-term follow-up period was 51.3 months, there was a good correlation between clinical status after two years of IT and after the long-term follow-up period, mainly in the excellent response group. Rev Argent Endocrinol Metab 51:8-14, 2014