Injection of Carbon Nanoparticles During Thyroid Cancer Surgery Helps Prevent Hypoparathyroidism

The injection of carbon nanoparticles during surgery to remove thyroid cancer and central lymph nodes is helpful to protect the parathyroid glands from damage and prevent temporary hypoparathyroidism, a recent study suggests.

The study, “Short and Long-Term Potential Role of Carbon Nanoparticles in Total Thyroidectomy with Central Lymph Node Dissection,” was published in the journal Scientific Reports.

Thyroid cancer is the most common tumor of the endocrine system, with papillary thyroid cancer accounting for more than 90% of all thyroid cancers. Between 20-50% of papillary thyroid cancers spread to the central neck lymph nodes (located near the thyroid), which increases the chance of cancer relapse.

Total or near-total surgical removal of the thyroid (called thyroidectomy) and central lymph nodes is a common procedure for the treatment of papillary thyroid cancer.

However, during this procedure, the parathyroid glands are at risk of being damaged, mainly due to inadvertent removal of the glands or interruption of their blood supply. This makes hypoparathyroidism —  a condition characterized by low levels of the parathyroid hormone — one of the most common (up to 37%) and severe complications of thyroidectomy.

Because the parathyroid hormone regulates blood calcium levels, hypoparathyroidism can cause hypocalcemia (low levels of calcium), leading to physical and mental disorders. Therefore, protecting the parathyroid glands and keeping their blood supply intact are main concerns during thyroid surgery.

Injection of harmless carbon nanoparticles during thyroid surgery has been shown to black-stain both the thyroid gland and lymph nodes around it, but not the parathyroid glands, highlighting its potential to help identify the parathyroids and guide the removal of lymph nodes.

However, their routine use in thyroid surgery is still controversial.

Researchers at the First Hospital of Jilin University, in China, evaluated the clinical benefits of using carbon nanoparticles during total thyroidectomy with bilateral removal of central lymph nodes in patients with papillary thyroid cancer.

They retrospectively analyzed the data of 406 patients (320 women and 86 men) who underwent this type of surgery from January 2010 to December 2012 at the First Hospital of Jilin University.

Patients’ mean age was 44.88 years, and carbon nanoparticles were used in the surgery of 106 of those patients. Individuals were followed-up for a period of 60 to 84 months after surgery.

Hypoparathyroidism and hypocalcemia were significantly less frequent in patients operated with carbon nanoparticles in a short period after surgery (day two, day five, and one month post-surgery), compared with those who were not. However, at six months post-surgery, these significant differences between the two groups disappeared.

Researchers noted this may be explained by the carbon nanoparticles-associated protection against parathyroid damage, which reduces the initial rates of hypoparathyroidism and hypocalcemia, and by the natural reconstruction of blood vessels damaged in surgeries conducted without carbon particles over the following six months, rescuing the glands’ function.

“The use of CN [carbon nanoparticles] significantly helped in identifying the parathyroid glands in surgery, which improved the postoperative … [parathyroid hormone] and serum calcium levels and decreased the incidence of transient hypoparathyroidism,” researchers wrote.

The use of carbon nanoparticles also significantly increased the number of total and malignant lymph nodes removed, suggesting this approach improves the removal of malignant central lymph nodes without increasing the chances of damaging the parathyroid glands.

However, after at least five years post-surgery, cancer relapse was not significantly different between the two groups of patients.

The team noted that, while the use of carbon nanoparticles was associated with some clinical benefits, it should not be exaggerated, since it could not improve the long-term frequency of hypoparathyroidism and cancer relapse in these patients.