NEW YORK (Reuters Health) - Primary tumor stage and number of lymph nodes examined may help doctors estimate the risk of occult nodal disease after papillary thyroid cancer surgery, a new paper suggests.
"This study is the first to provide objective guidance for evaluating the adequacy of lymph node yield in papillary thyroid cancer management. The actual number of lymph nodes (that need) to be examined to estimate the risk of occult disease is surprising, given the fact that the numbers are higher than often surgically removed," said coauthor Dr. Julie Ann Sosa, Chief of Endocrine Surgery at Duke University in Durham, North Carolina and leader of the endocrine neoplasia diseases group in the Duke Cancer Institute and the Duke Clinical Research Institute.
"These results can help guide decisions, based on the patient's primary tumor, regarding how comprehensive a surgical resection should be, whether to give radioactive iodine after surgery, and how frequently to surveil the patient for disease recurrence," Dr. Sosa told Reuters Health by email. "We hope this becomes a useful clinical tool for counseling patients regarding their individual disease risk and allowing them to participate more actively in their treatment decisions."
As reported online August 15 in the Journal of Clinical Oncology, Dr. Sosa and her colleagues used roughly 15 years of data from the National Cancer Database to examine the distribution of nodal positivity in adults with localized 1-cm or greater papillary thyroid cancer. All patients underwent thyroidectomy and had one or more lymph nodes surgically examined and no evidence of distant metastases.
The researchers used a beta-binomial distribution to estimate the probability of occult nodal disease as a function of the tumor stage and the number of lymph nodes examined.
Overall, 38,653 patients had node-positive disease and 40,071 were node-negative. When a single node was examined, the estimated probability of falsely identifying a patient as node-negative was 53%; but when more than six lymph nodes were examined, the probability dropped below 10%.
To rule out occult nodal disease with 90% confidence, 6, 9, and 18 nodes would need to be examined for patients with T1b, T2, and T3 disease, respectively. Sensitivity analyses limited to patients likely to undergo prophylactic central neck dissection resulted in 3, 4, and 8 nodes necessary to provide comparable lymph node evaluation.
"From a biostatistical perspective, this is a methodologically rigorous study. It is retrospective, so prospective validation would be ideal, but that may be impossible due to the indolent nature of papillary thyroid cancer," Dr. Sosa advised.
Senior coauthor Dr. Terry Hyslop, Director of Biostatistics at the Duke Cancer Institute, said in an email that the results are consistent with those seen in other cancers and make numerical sense.
"Numerous cancers now have guidelines in place to inform clinicians on the recommended number of nodes to remove and evaluate," she noted.
"As in all models, we must make assumptions for computational feasibility, such as a constant rate of accuracy of evaluating nodes," Dr. Hyslop added. "We are working on developing the model further so we may be more flexible with the number of assumptions required. It will be interesting to see the impact this may have on our findings."
Dr. David M. Cohan, assistant professor of oncology in the Department of Head and Neck Surgery at Roswell Park Cancer Institute in Buffalo, New York told Reuters Health by email that the study "highlights a few of the emerging and controversial concepts in differentiated thyroid cancer management. For example, when, if ever, is prophylactic central neck dissection indicated? When do the risks of central neck dissection justify, or not justify, the benefits?"
"It is my hope that this research will generate more nuanced conversations between thyroid cancer patients and their health care providers," added Dr. Cohan, who was not involved in the study.
A P30 Cancer Center Support Grant from the National Cancer Institute and Duke University departmental funds supported this study.
SOURCE: http://bit.ly/2bSffcj
J Clin Oncol 2016.
Δεν υπάρχουν σχόλια:
Δημοσίευση σχολίου