Prognostic factors in patients with Hürthle cell neoplasms of the thyroid.

BACKGROUND: Hürthle cell neoplasms, often considered a variant of follicular thyroid neoplasms, represent 3% of thyroid carcinomas. Only a handful of publications have focused on the biologic behavior, prognostic factors, and treatment outcomes of Hürthle cell carcinoma. The objective of the current study was to identify the clinical and pathologic features of Hürthle cell carcinomas that predict disease progression or death.

METHODS: The authors reviewed medical records of patients who were treated for Hürthle cell carcinoma (HCC) and Hürthle cell adenoma (HCA) at The University of Texas M. D. Anderson Cancer Center from March 1944 to February 1995, including follow-up information. The pathologic diagnosis was confirmed by one of the authors.

RESULTS: The authors identified 127 patients with Hürthle cell neoplasms, 89 patients with HCC and 38 patients with HCA. Seven patients with HCC had foci of anaplastic thyroid carcinoma. Survival for this subgroup was worse compared with the overall group and was analyzed separately. The HCC group was significantly older (age 51.8 years vs. age 43.1. years) and had larger tumors (4.3 cm vs. 2.9 cm) compared with the HCA group. No differences were seen in gender or previous radiation exposure. Forty percent of patients in the HCC group died of thyroid carcinoma, whereas no patients in the HCA group died of the disease. There has been no improvement in all-cause and disease specific mortality in the past 5 decades for patients with these neoplasms. Conventional staging systems predicted mortality with minor differences. Of the patients with known metastasis, 38% showed radioiodine uptake. Univariate analysis identified older age, higher disease stage, tumor size, extraglandular invasion, multifocality, lymph node disease, distant metastasis, extensive surgery, external beam radiation therapy, and chemotherapy as factors that were associated with decreased survival. Tumor encapsulation was associated with improved survival. Although radioactive iodine treatment had no overall effect on survival, subgroup analysis showed that patients who received radioactive iodine for adjuvant ablation therapy had better outcomes compared either with patients who did not receive radioactive iodine or with patients who received radioactive iodine as treatment for residual disease. Multivariate analysis indicated that older age and larger tumor size predicted worse survival through an association with worse behaving tumors (multifocal, less encapsulated, and with extraglandular invasion). The decreased survival in patients with lymph node metastases may be explained by its association with distant metastases. The association of extensive surgery, external beam radiation therapy, and chemotherapy with worse survival also disappeared once those factors were analyzed together with other prognostic factors, such as distant metastases.

CONCLUSIONS: Several clinical and pathologic prognostic factors were identified in patients with HCC and HCA. Older age and larger tumor size predicted reduced survival. Radioactive iodine therapy may confer a survival benefit when it is used for adjuvant ablation therapy, but not when residual disease is present. The authors could not demonstrate a survival benefit for the use of extensive surgery, external beam radiation therapy, or chemotherapy.