Objective: This investigation aimed at exploring the prospects of a cure for persistent medullary thyroid cancer (MTC) stratified by basal calcitonin levels before reoperation and the number of lymph node metastases previously removed at outside facilities.
Background: There is no evidence-based information supporting the balance of surgical benefit and risk in persistent MTC.
Methods: This retrospective study of 334 patients with persistent MTC referred to a tertiary surgical center, who were compared with 367 patients with previously untreated MTC referred to that institution during the same time period, evaluated biochemical cure rates after systematic lymph node dissection.
Results: The relationship between the incremental serum calcitonin level before reoperation and the number of lymph node metastases at reoperation and biochemical cure was strong after previous removal of 0 (r = 0.74 and 77%-0%) and 1 to 5 lymph node metastases (r = 0.61 and 60%-0%) elsewhere. It disappeared once more than 5 lymph node metastases had been cleared at other hospitals (nonsignificant and 5%). When serum calcitonin levels were 1000 pg/mL or lower before reoperation, biochemical cure rates were 44% (59 of 133 patients) and 18% (12 of 65 patients) after previous removal of 0 and 1 to 5 lymph node metastases, respectively. These rates plummeted to 5% (2 of 43 patients) after a previous clearance of more than 5 lymph node metastases. When serum calcitonin levels exceeded 1000 pg/mL before reoperation, a biochemical cure was exceptional (1%; 1 of 76 patients).
Conclusions: With serum calcitonin levels of 1000 pg/mL or lower before reoperation and the previous removal of 5 or fewer lymph node metastases, systematic lymph node dissection seems worthwhile for persistent MTC. These findings will need to be validated in independent series before being adopted more widely as a new standard of care.