BACKGROUND
Papillary thyroid cancer is the most common type of thyroid cancer. The vast majority of thyroid cancers are located in the right or left lobe of the thyroid. Only a small number of thyroid cancers are located in the isthmus, the thin middle part of the thyroid that connects the lobes on both sides. Cancers in this location may have have a higher risk of spreading beyond the thyroid. In recent years, there has been a growing emphasis on reducing the extent of surgery for low-risk thyroid cancer, since the outcomes are similar while the complication rates are lower. Traditionally, surgeons removed the entire thyroid (total thyroidectomy) for high risk cancers or one lobe (lobectomy) for small cancers that are limited to 1 lobe. However, there are no clear guidelines on how much thyroid tissue should be removed when the thyroid cancer is only in the isthmus.

Recent studies suggest that removing only the isthmus (isthmusectomy) may be an alternative for some patients when the cancer is limited to the isthmus. Researchers designed this study to look at which option works best for a single thyroid cancer located only in the isthmus.

THE FULL ARTICLE TITLE
Lee S et al. Comparative study of clinical outcomes for total thyroidectomy/lobectomy and isthmusectomy in patients with isthmic papillary thyroid carcinoma. Thyroid 2025;35:1322-1330; PMID: 41020703.

SUMMARY OF THE STUDY
Researchers reviewed records from 345 patients treated between 2013 to 2022 at 2 major hospitals in South Korea. These patients had a single, small, low-risk papillary thyroid cancer located in the isthmus and were treated with total thyroidectomy, lobectomy, or isthmusectomy. Patients with very aggressive cancer types, more than one cancer, or known extension of the cancer beyond the thyroid were excluded. Patients were considered candidates for isthmusectomy if the cancer was less than 4 cm and showed no clear extension beyond the thyroid gland. Researchers combined the patients who had total thyroidectomy or lobectomy into one group and compared them with the patients who had isthmusectomy. The groups were carefully matched, so the groups were very similar in age, sex, cancer type, size, and extent, as well as other factors that affect cancer behavior, such as BRAF gene mutation or Hashimoto thyroiditis.

The main outcomes that were looked at were cancer return in the lymph nodes, thyroid, or other parts of the body. The study also looked at complications of surgery, such as low calcium levels, vocal cord paralysis, or the need to take thyroid hormone.

There were 345 patients with a single papillary thyroid cancer in the isthmus who met the inclusion criteria. After matching similar patients, 85 patients were included in each group. Patients were very similar at baseline between the groups. The average age was 48.5 vs 47.9 years; most patients were female (76.5% vs 77.7%); and the average cancer size was 0.8 cm. More than 60% had minimal extension beyond the thyroid, and about 10% had more than one cancer. These were patients who had hidden cancer in the lymph nodes or microscopic extension beyond the thyroid gland found after surgery. This situation is common in real-world practice, as these findings are sometimes too small to detect before surgery. Patients were followed for about 5 years.

There was no evidence of cancer return in either group during this time. However, patients who had a thyroidectomy or lobectomy had more complications after surgery. Temporary low calcium occurred in 14% and permanent low calcium in 1.2%, and temporary vocal cord paralysis in 3.5% while none of the patients who had isthmusectomy had these complications. The need for thyroid hormone replacement and the required dose were also higher in the total thyroidectomy/lobectomy group (90.6%) than in the isthmusectomy group (34%).

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
The findings of this study show that isthmusectomy appears to be a safe and effective surgical option for carefully selected patients with small papillary thyroid cancers limited to the isthmus. This is important for patients since less surgery in the right situation can lower the risk of complications, improve quality of life without increasing the risk of cancer coming back. Longer follow-up is still needed to confirm these findings, and decisions about surgery should be tailored to each patient.

— Ebru Sulanc, MD

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