BACKGROUND
Thyroid cancer is the fastest rising cancer in women. Indeed, autopsy studies have shown that up to 1/3rd of adults who die of other causes will have a small (<1 cm) papillary thyroid microcarcinoma within their thyroid gland that was not identified while the individual was alive. This is part of the reason that the American Thyroid Association guidelines for the management of thyroid nodules and cancer do not recommend biopsy of small thyroid nodules (<1-1.5 cm). Also, at the time of surgery for larger nodules that have been diagnosed as papillary thyroid cancers, up to 30% end up being diagnosed as papillary thyroid microcarcinomas.

The guidelines recommend 2 possible options for management of papillary thyroid microcarcinomas: 1) thyroid lobectomy as a definitive treatment, provided there is no evidence spread outside of the neck or the patient is at high risk or 2) active surveillance, which is monitoring them over time with ultrasound and physical exam and avoiding surgery. Active surveillance is an option due to the overall low risk of these cancers. However, a small minority of papillary thyroid microcarcinomas do have aggressive features on pathology and may not be low risk.

The aim of this study was to determine how common these microcarcinomas are and how many have aggressive features using a large database of patient with papillary thyroid microcarcinomas who also had surgery.

THE FULL ARTICLE TITLE
Al-Qurayshi Z et al 2020 Wolf in sheep’s clothing: Papillary thyroid microcarcinoma in the US. J Am Coll Surg 230:484–491. PMID: 32220437.

SUMMARY OF THE STUDY
This study used the National Cancer Database from 2010 to 2014 and analyzed adult patients with a primary diagnosis of papillary thyroid microcarcinoma who had undergone thyroid surgery.

Independent factors assessed were age, sex, race, type of thyroid surgery, lymph node involvement, whether they received radioactive iodine therapy and the total size of the papillary thyroid microcarcinoma. The association between each of these independent factors and the risk of aggressive features was tested and overall survival was determined.

The study group consisted of 30,180 patients, of whom 5628 (18.7%) had at least one aggressive feature (spread to lymph nodes, extension outside of the thyroid or into the blood vessels or spread of the cancer outside of the neck.) The average follow-up was ~39 months. The 5-year overall survival was 98.5%, which was similar to the overall survival of patients without aggressive features (98.4%). Most patients (82%) were otherwise healthy. The majority of patients (82.6%) underwent a total thyroidectomy, 52.2% underwent concomitant neck dissection and 25.4% received radioactive iodine therapy.

Patients with aggressive features were more likely to be young (<55 years old), male, white and treated in hospitals that see a lot of thyroid cancer patient. With regard overall survival, spread to either the central or lateral lymph nodes, as well as extension outside of the thyroid and spread outside of the neck were associated with decreased survival.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study shows that ~19% of papillary thyroid microcarcinomas have aggressive features on pathology. Based on these results, the authors suggest a lobectomy is the best option to manage these patients. However, the presence of aggressive features did not significantly alter overall survival, which is excellent. Longer studies are needed to confirm the survival results. Since active surveillance requires ongoing regular monitoring with ultrasound and physical exam and leads to surgery with any changes, both lobectomy and active surveillance remain reasonable options for management of papillary thyroid microcarcinomas. Patients and doctors show discuss these options to determine the best option for any individual patient.

— Alan P. Farwell, MD

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