Task Force Recommends Active Surveillance for Many Low-Risk Papillary Thyroid Microcarcinoma Patients

Active surveillance (AS) can be a safe and appropriate management strategy for patients with T1aN0M0 low-risk papillary thyroid microcarcinoma (PTMC), though the decision to use the strategy requires multidisciplinary teams and patient input, according to a new report.

Thyroid cancer has become more and more common in the world, driven largely by better detection of small papillary thyroid cancers (PTCs). Tools such as ultrasonography (US) and US-guided fine-needle aspiration cytology have made it possible to detect cancers that otherwise might never be detected or might only be detected in an autopsy. Although better detection is a positive step, it also raises the specter of overdiagnosis and overtreatment.

AS has been gaining consideration as an acceptable management strategy for low-risk PTMC although various concerns still exist. Thus, a task force of the Japan Association of Endocrine Surgery was created to make a set of recommendations on the indications and strategies for implementing AS for adult patients with low-risk PTMC. The study authors, led by Iwao Sugitani, MD, PhD, of the Nippon Medical School Graduate School of Medicine, in Japan, outlined some of the key considerations when evaluating patients with PTMC to determine the appropriateness of AS.

The task force noted that the development of routine AS in these patients can be traced back to 2 Japanese hospitals, Kuma Hospital and the Cancer Institute Hospital, which in the mid-1990s began prospective clinical studies of AS in PTMC. Outcomes were favorable: few patients experienced cancer growth or lymph node metastases, and no patients developed distant metastases or died of thyroid cancer.

Those data led to changes in Japanese clinical guidelines in 2010, and AS was added as an alternative management strategy by the American Thyroid Association in 2015.

Yet, not every physician or patient has been comfortable with the strategy. Sugitani said the idea of AS can be anxiety inducing for patients and physicians alike.

“Less experienced physicians and surgeons tend to feel anxious about the validity of AS and recommend immediate surgery even for very low risk patients,” he told Targeted Oncology.

Sugitani said surgery might seem like the easier and quicker option, though he said it should not be seen as eliminating the need for active follow-up.

“In theory, even patients who underwent surgery need long-term postoperative follow-up,” he said; “however, in reality, many physicians terminate it several years after surgery when lobectomy is performed and thyroid hormone supplementation is not necessary.”

In the consensus statements, the task force explained that AS requires considerable manpower and engagement from a multidisciplinary team.

Extrathyroidal extension (ETE) and lymph node metastases (LMN) should be evaluated using US. Chest x-ray CT is not necessary at the start of AS, the authors said, though it may be necessary if the disease progresses.

One important factor in determining the appropriateness of AS is the age of the patient. Sugitani and colleagues wrote that older patients are ideal candidates for AS, since it is less likely they will live long enough for the slow-developing cancer to progress. However, they said young patients should not necessarily be ruled out for AS, since, even among patients diagnosed in their 20s, the rate of lifetime progression is less than 50%.

In general, Sugitani said their analysis suggests “lax” inclusion criteria for AS. “For example, many physicians usually hesitate to recommend AS for patients with multiple PTMCs, young age, tumor simply close to the dorsal side of the thyroid, rich vascularity or slightly bigger than 1 cm,” he said. “Our paper showed evidence that those patients could still be candidates for AS.”

Sugitani and colleagues wrote that US evaluations should take place every 6 months for the first 1 to 2 years, followed by annual check-ups. They said there are no data to suggest a limit to the duration of AS; it could therefore be considered a lifetime strategy if nothing in the patient’s case changes.

As physicians evaluate patients over time, Sugitani and colleagues said maximal tumor diameter is the optimal method of growth evaluation. “Enlargement” should be defined as an increase of 3 mm or more, though they said enlargement does not always warrant surgery.

The authors said evidence is lacking for a number of common strategies. For example, suppression of tumor stimulating hormone (TSH) has been proposed as a strategy for limiting tumor enlargement; however, Sugitani said there are insufficient data to say that the strategy works. If used, Sugitani and colleagues said it may be best to keep TSH levels at the low to normal range.

Going forward, the task force highlighted 2 key areas where additional research is particularly needed. One is molecular markers, which, if identified, could give physicians a more reliable indication of PTMC behavior. The other area where Sugitani and colleagues would like to see more research is in patient-reported outcomes. They noted that the AS strategy can be anxiety producing; thus, further investigation into the psychological and quality-of-life impacts of the strategy is appropriate.

_Reference:

_{Sugitani I, Ito Y, Takeuchi D, et al. Indications and Strategy for Active Surveillance of Adult Low-Risk Papillary Thyroid Microcarcinoma: Consensus Statements from the Japan Association of Endocrine Surgery Task Force on Management for Papillary Thyroid Microcarcinoma. Thyroid. Published online November 2, 2020. doi:10.1089/thy.2020.0330}