OBJECTIVE. To study the clinical parameters and treatment outcome of medullary thyroid carcinoma in Hong Kong Chinese patients.

DESIGN. Retrospective study.

SETTING. Regional oncology unit, Hong Kong.

PATIENTS. Patients with medullary thyroid carcinoma who were identified among 1656 patients with thyroid malignancies seen in a single institute in Hong Kong from January 1960 to June 2003.

MAIN OUTCOME MEASURES. Ten-year cause-specific survival, locoregional failure-free survival, and distant metastasis failure-free survival.

RESULTS. Twenty-two (1.3%) patients with medullary thyroid carcinoma were identified. The mean age at diagnosis was 43.7 (standard deviation, 16.5) years. The sex ratio was 1:1. The 10-year cause-specific survival, locoregional failure-free survival, and distant metastasis failure-free survival were 75.4%, 82.0%, and 62.4%, respectively. Lymph node metastasis was present in seven (31.8%) patients at diagnosis. Distant metastasis developed in nine (40.9%) patients: lung, 3 (13.6%); bone, 5 (22.7%); liver, 2 (9.1%); mediastinum, 4 (18.2%). Seven (31.8%) patients died of distant metastasis. Mediastinal (n=3) and bone metastases (n=3) were important causes of death. Genetic study confirmed multiple endocrine neoplasia type 2A in 3 (25.0%) of 12 patients who all had bilateral and multifocal diseases. Younger age (<45 years) was associated with better survival, better locoregional control, and less distant metastasis. Patients with pT1N0 disease (n=3) had an excellent prognosis: all were disease-free following total thyroidectomy. Among eight patients who received external radiation therapy, seven achieved good locoregional control. In seven patients with lymph node metastasis, external radiation therapy gave 100% (4/4) locoregional control compared with 33.3% (1/3) in those without external radiation therapy. Chemotherapy using dacarbazine and 5-fluorouracil was tried in three patients with poor response.

CONCLUSIONS. Early stage (T1N0) medullary thyroid carcinoma is associated with a very good prognosis. Postoperative external radiation therapy can achieve good locoregional control in patients with lymph node metastasis or locally advanced disease.

Key words: Carcinoma, medullary; Multiple endocrine neoplasia; Radiotherapy; Thyroid neoplasms

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