Prediction of biochemical cure in patients with medullary thyroid cancer

Background: The impact of number of node metastases versus metastatic lymph node ratio versus AJCC node category on biochemical cure in medullary thyroid cancer (MTC) is not well defined. Methods: Multivariable logistic regression analysis was used to determine clinical and histopathological variables that contribute to biochemical cure in node-positive MTC. Results: Some 584 of 1026 patients with MTC underwent systematic lymph node dissections for node-positive disease; 27 center dot 4 per cent (54 of 197) were biochemically cured after the initial operation and 13 center dot 5 per cent (42 of 310 patients) after repeat surgery. Cured patients had significantly less extrathyroid extension (11-14 versus 33 center dot 2-55 center dot 6 per cent), fewer lymph node metastases (median 2-4 versus 12-16), a lower metastatic lymph node ratio (median 0 center dot 05-0 center dot 08 versus 0 center dot 23-0 center dot 28), and were less likely to have AJCC pN1b disease (56-76 versus 89 center dot 9-91 center dot 6 per cent) and distant metastases (0 versus 28 center dot 4-37 center dot 1 per cent) than patients who were not cured. Biochemical cure curves advanced steadily up to 7-12 node metastases and a metastatic lymph node ratio of 0 center dot 33, eventually levelling off after 16-17 node metastases and metastatic lymph node ratios of 0 center dot 45-0 center dot 65. In logistic regression analysis, number of lymph node metastases (odds ratio (OR) 17 center dot 24 for more than 20 metastases, OR 5 center dot 28 for 11-20 metastases, OR 2 center dot 22 for 6-10metastases), preoperative basal serum calcitonin (OR6 center dot 24 for over 1000 pg/ml), reoperation (OR 5 center dot 34) and extrathyroid extension (OR 2 center dot 42) independently predicted failure to reach biochemical cure. Conclusion: Number of lymph node metastases, unlike metastatic lymph node ratio or AJCC node category, determines likelihood of biochemical cure after initial and repeat surgery for node-positive MTC.