BACKGROUND
Thyroid cancer is common. Fortunately, the prognosis is excellent, and most patients do very well. Because of this, the management of thyroid cancer has changed significantly in recent years. Traditionally the thyroid gland was removed with surgery (total thyroidectomy) and then radioactive iodine treatment was used to destroy any remaining thyroid cancer cells. This approach often removed all the cancer but could cause side effects that were not necessary for every patient. There are several factors that are considered when thyroid cancer is diagnosed, such as size, location, presence of spread outside of the thyroid, or the cell type that makes the cancer. Based on these factors, some cancers are considered low risk. Studies showed that a significant number of low-risk papillary thyroid cancers grow slowly. Because of this, they may never cause health problems or shorten a person’s life. As an alternative to surgery, some patients with low risk thyroid cancers can be followed with ultrasound and blood tests if there are no other concerning factors. Surgery can be done later if cancer grows or spreads. This is called active surveillance, and it became accepted management, initially for cancers less than 1 cm and more recently for some cancers measuring less than 1.5 cm. The patients did well over time and many never needed surgery.

The cancer size has been one of the main factors used to decide whether active surveillance is appropriate. It was assumed that larger cancers would be more likely to grow or spread, but this assumption has not been studied in detail. In this study, the researchers evaluated the safety and clinical outcomes of active surveillance in patients with papillary thyroid cancers measuring more than 1.5 cm.

THE FULL ARTICLE TITLE
Sanchez LP, et al. Active surveillance in papillary thyroid cancer with primary tumors greater than 1.5 cm. Head Neck. Epub 2026 Apr 16; doi: 10.1002/hed.70279. PMID: 41992678.

SUMMARY OF THE STUDY
Researchers at Memorial Sloan Kettering Cancer Center reviewed the records of 45 patients who had thyroid cancer completely inside the thyroid, between 1.6 and 2.9 cm, and were managed with active surveillance. The patients had a neck ultrasound every 6-12 months. The average follow-up was 50 months. Progression of the cancer was defined as a 3 mm or more increase in the longest measurement, more than 70% increase in volume, or newly found lymph nodes in the neck. They also looked at outcomes of patients who later had surgery due to progression.

Only 6 patients (13%) had significant increase in cancer volume, 5 (11%) had an increase in the longest diameter, and 5 (11%) had newly detected cancer spread to neck lymph nodes. Among these patients, 9 (20%) eventually had surgery. Patients who had delayed surgery had excellent outcomes — no cancer was left, cancer did not return and none of them died due to cancer. Cancers measuring 2 cm or more behaved very similarly to the cancers between 1.6-1.9 cm; there was no difference in how fast they grew, whether cancer appeared in lymph nodes, or whether they needed surgery.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study suggests that active surveillance can be a safe alternative to surgery in some carefully selected patients with thyroid cancers larger than 1.5 cm. Some cancers grew or spread to lymph nodes; however, this did not appear to be linked to the cancer size. Patients had similar outcomes whether they had larger or smaller cancers and patients who needed surgery later had excellent results. As a caution, this was a small study from a single, specialized cancer center, so larger studies with longer follow up are needed before these findings can be applied widely. However, the results suggest that cancer size alone doesn’t predict how a cancer will behave, and careful monitoring doesn’t seem to lower the chance of a cure if surgery is needed later. Cancer size may still matter, but it shouldn’t be the deciding factor when choosing between surgery and active surveillance.

— Ebru Sulanc, MD

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