BOSTON – Central lymph node dissection may not be necessary in patients with small parathyroid carcinomas, results of a data review suggest.
Among 405 U.S. patients treated in the last two decades for parathyroid carcinomas, disease-specific mortality and degree of local tumor invasion did not differ depending on nodal involvement, reported Dr. Kun-Tai Hsu, an associate research specialist in the surgery department at the University of Wisconsin, Madison.
Patients with tumors greater than 3 cm in diameter and distal metastasis had worse disease-specific mortality, and larger tumors were significantly more likely to be associated with positive lymph nodes, Dr. Hsu reported at the annual meeting of the American Association of Endocrine Surgeons.
Dr. Kun-Tai Hsu
The findings raise the question of whether central lymph node dissection is necessary for all patients with parathyroid carcinomas, but "our conclusions may not translate directly into definitive recommendations," said Dr. Hsu, who advised further study of whether patients with tumors larger than 3 cm may benefit from lymph node dissection.
Parathyroid carcinomas are rare cancers, accounting for 0.005% of all malignancies and less than 1% of primary hyperparathyroidism. The current standard of therapy is en bloc removal of the parathyroid tumor and ipsilateral lobectomy, isthmusectomy, and central lymph node dissection.
Over at least 5 years of follow-up, neither tumor size nor lymph node status was significantly predictive of outcomes in an earlier retrospective study of 286 patients treated in the 1980s and 1990s.
In addition, a 2006 study using data from the Surveillance, Epidemiology and End Results (SEER) database showed a significant increase in the incidence of this malignancy from 1988 through 2003. The authors identified younger age, female sex, more recent diagnosis, and absence of distant metastases as favorable prognostic factors (Cancer 2007;109:1736-41).
What the previous studies could not answer, however, was whether lymph node metastases were associated with worse disease-specific mortality and whether central lymph node dissection might improve survival in patients with parathyroid carcinomas, Dr. Hsu noted.
He and his colleagues queried SEER for disease-specific survival outcomes and lymph-node status of all patients treated in the United States for parathyroid carcinomas from 1988 through 2010.
They identified 212 female and 193 male patients. Among all patients, 112 (27.7%) had tumors 3 cm or greater, and 12 (3%) had positive lymph nodes. Median follow-up was 68 months.
In a multivariate analysis of disease-specific mortality predictors adjusted for sex and age only, tumors 3 cm or greater and the presence of metastasis were predictive of worse survival, with respective hazard ratios of 5.35 (P = .01) and 45.1 (P less than .01).
Similarly, an analysis adjusted for sex, age, and year of diagnosis showed that tumor size but not age or sex significantly predicted lymph node metastasis (HR, 19.48; P = .02)
A comparison of outcomes between patients with and without lymph node examinations found no differences in disease-specific mortality by sex, age, year of diagnosis, tumor size, local invasion, or metastasis. Significant predictors of disease-specific mortality in this analysis included surgery type (parathyroidectomy, en bloc excision, or debulking), the use of radiation, and white race.
Dr. Hsu noted that the study was limited by its retrospective design, lack of information on other significant clinical variables, lack of detailed follow-up data, and the possibility of misclassification or miscoding of cases.
He acknowledged that uncertainty about the diagnosis is a drawback to SEER-based studies, but that given the rarity of the disease, SEER data are the most reliable source of information.
The study was supported by the Wisconsin Surgical Outcomes Research Program. Dr. Hsu reported having no relevant disclosures. Study coauthor Dr. Rebecca Sippel is a member of this publication’s editorial advisory board.