BACKGROUND
Papillary thyroid cancer is the most common thyroid cancer. Many of these cancers are small (<1 cm) and are referred to as microcarcinomas. Papillary thyroid microcarcinomas are common, particularly with increasing age. Most papillary thyroid microcarcinomas are considered low risk as they are very slow growing. Because of this, papillary thyroid microcarcinomas are usually managed with either active surveillance (following the cancers by ultrasound rather than immediate surgery) or with removal of the lobe containing the cancer (lobectomy). Oftentimes, these microcarcinomas are considered “cured” after lobectomy. However, a subgroup of papillary thyroid microcarcinomas are higher risk and can spread outside the neck. Additionally, these cancers can recur after surgery. Identification of such patients at diagnosis may identify those that would benefit from more intensive management.

The aim of this study was to evaluate the association between the spread of cancer to the lymph nodes in the neck in patients with papillary thyroid microcarcinomas and future risk of cancer recurrence.

THE FULL ARTICLE TITLE
Ruan J et al 2023 Lateral lymph node metastasis in papillary thyroid microcarcinoma: A study of 5241 follow-up patients. Endocrine. Epub 2023 Aug 7. PMID: 37596455.

SUMMARY OF THE STUDY
This is a study of 5241 patients with papillary thyroid microcarcinoma from China between 1997 and 2016. Aggressive subtypes of papillary thyroid cancer and patients with less than 1 year of follow-up were excluded from the study. Patients were monitored for cancer recurrence using serum thyroglobulin levels and neck ultrasonography. Spread of the cancer to the lymph nodes were confirmed either after surgical removal or by a positive radioactive iodine whole-body scan. The patients were predominantly female (76%) and young (79% were less than 55 years of age), and the average cancer size was 0.6 cm. Cancer was found in lymph nodes in the central neck in 26% cases and in the lateral neck in 2.5% of cases. Average postoperative follow-up was 60 months.

During follow-up, cancer recurrence occurred in 114 of 5241 (2.2%) patients. Sites of recurrence were the thyroid bed (41), lymph nodes (69) and distant sites (3). There were 24 patients who died but only 1 of these deaths was associated with their thyroid cancer (0.05%). The 5-year cancer-free survival was 98.9% if there was no cancer in the lymph nodes at the time of initial surgery, 96% if there was cancer in the lymph nodes in the central neck at the time of initial surgery and 87% if there was cancer in the lymph nodes in the lateral neck at the time of initial surgery. Thus, the presence of cancer in the lymph nodes at the time of initial surgery was the only significant predictor of cancer recurrence. There was a 3-fold increase risk of cancer recurrence if there was cancer in the lymph nodes in the central neck at the time of initial surgery and ~11-fold increase risk of cancer recurrence if there was cancer in the lymph nodes in the lateral neck at the time of initial surgery.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study shows that the majority of patients with papillary thyroid microcarcinoma have a very low risk of cancer recurrence (2.2%) and the vast majority of patients with cancer recurrence (94%) had cancer identified in lymph nodes at the time of initial surgery. The presence of cancer in the lateral neck nodes at diagnosis was the strongest predictor of future recurrence. This study suggests that patients with papillary thyroid microcarcinoma without lymph node involvement can be followed less intensely while those with any lymph node involvement should continue to be followed closely. This study also suggests that all patients with papillary cancer should have a lateral neck node survey by ultrasound prior to surgery to better direct the surgery and to plan for future care.

— Alan P. Farwell, MD

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