Hypoparathyroidism Risk Increases After Thyroid, Lymph Node Surgery, Study Reports

Central lymph node dissection (CLND), or the removal of lymph nodes in the neck, increases the risk of permanent hypoparathyroidism in people with papillary thyroid cancer (PTC) who are treated by total thyroidectomy — surgery to remove the thyroid gland — a nationwide study from Sweden reports.

The study, “Central lymph node dissection and permanent hypoparathyroidism after total thyroidectomy for papillary thyroid cancer: population-based study,” was published in the British Journal of Surgery.

PTC is the most common form of thyroid cancer. In 50% to more than 75% of PTC patients, the cancer spreads to the neck lymph nodes, located near the thyroid, increasing the risk of cancer relapse. The standard treatment for PTC patients with large tumors is total or near-total thyroidectomy, with or without CLND.

Previous studies have suggested that CLND decreases the cancer recurrence rate and increases survival in thyroid cancer patients. However, total thyroidectomy with CLND also may increase the risk of hypoparathyroidism, studies have shown.

Due to these risks, thyroidectomy without CLND is recommended for PTC patients with small tumors or in the absence of malignancy. Still, the association between CLND and permanent hypoparathyroidism remains unclear.

Now, researchers at Lund University in Sweden sought to determine the relationship between CLND and permanent hypoparathyroidism in people with non-advanced PTC tumors (stage pT1 -3).

Using the Scandinavian Quality Register for Thyroid, Parathyroid and Adrenal Surgery, the team collected data from 2004 to 2014 on adults with PTC who underwent thyroidectomy with or without CLND. Patients with advanced tumors and those who had previously had thyroid or parathyroid surgeries were excluded from the study. The remaining patients were divided into groups based on treatment types: thyroidectomy alone (TT) or thyroidectomy with concurrent CLND.

A total of 722 patients — 568 women and 154 men, with a median age of 47 — were included in the study. Of those patients, 36.7% had TT and 63.3% underwent both TT and CLND. Men were more likely to have had the double procedure than women (77.3% vs. 59.5%). Most participants receiving TT and CLND (87.3%) underwent surgery because of suspected malignancy, compared with just 13.6% of TT patients.

Reimplantation of the parathyroid gland — done after incidental damage or the removal of the gland during surgery — was performed in 46.1% of patients. The individuals having reimplantation included 56.9% of those who underwent TT and CLND, and 27.5% of participants receiving TT alone. Permanent hypoparathyroidism was reported in 6% of these patients, indicating that parathyroid reimplantation did not prevent hypoparathyroidism.

An analysis of various potential risk factors, including age, sex, tumor category, treatment type, and lymph node status, found that TT with CLND was associated with an increased risk of hypoparathyroidism. In this group, the absence of cancer in the lymph nodes (node negativity) was associated with permanent hypoparathyroidism post-surgery. This association may be due to accidental gland removal resulting from the similarity in appearance of healthy lymph nodes and parathyroid glands, the team said.

“The increased risk of permanent hypoparathyroidism after CLND must be weighed against the potential benefits of the procedure,” the researchers wrote. “Node negativity is associated with a higher risk of permanent hypoparathyroidism, suggesting an increased risk of permanent hypoparathyroidism in patients who undergo prophylactic CLND.”

Among the study limitations were the exclusion of patients outside of the SQRTPA and a lack of information about the patients’ parathyroid hormone level, the number of surgeries performed by individual surgeons, and the scope of the CLNDs performed.