A new study regarding the risk of occult nodal disease in patients undergoing surgery for papillary thyroid cancer offers an empiric framework to help surgeons determine how many lymph nodes (LNs) must be dissected and analyzed to assess the risk of residual disease.

In the study, researchers from the Duke Clinical Research Institute (DCRI) and Duke Cancer Institute (DCI) strived to establish objective, quantifiable information regarding the minimum number of LNs analyzed around a tumor without putting the patient at unnecessary risk. The retrospective study was published in the Journal of Clinical Oncology. 

“In these procedures, a lot is left to the surgeon. If the tumor is large or there’s obvious evidence that the cancer is in the LNs, you take them out,” says author Julie Ann Sosa, MD, chief of endocrine surgery and leader of the Endocrine Neoplasia Diseases group at the DCRI and DCI.

“If there is no evidence of obvious invasion, you can remove them preventively, but you might not have to,” Sosa says.

“That’s the quandary faced by the entire health care team: for the surgeon, whether to take the LNs out; for the endocrinologist, whether to give radioactive iodine, in part, based on the information obtained about LNs during surgery; and, for the patient, whether the information and treatment will result in better survival.”

Duke researchers analyzed almost 39,000 cases of papillary thyroid cancer with nodal spread. Accessed through the National Cancer Database, the cases occurred between 1998 and 2012. Each patient had undergone thyroidectomy, at which time at least 1 LN was examined.

Researchers estimated the number of LNs that would need to be dissected at different disease stages to predict the absence of occult residual nodal disease with 90% confidence:

• For stage T1b, dissection and testing of 6 LNs
• For stage T2, dissection and testing of ≥ 9 LNs
• For stage T3, dissection and testing of ≥ 18 LNs

“We are trying to quantify the risk,” says senior author Terry Hyslop, PhD, director of biostatistics at DCI. “We don’t know the exact probability within each person, but this is based on patterns within a large set of data.”

In prophylactic dissection of central neck LNs that may contain cancerous tissue not visible in presurgical imaging, the removal and testing of 3 to 8 LNs is recommended with 90% confidence that no tumor is left behind, depending on the stage of disease.