BACKGROUND
The formation of abnormal growths in the thyroid gland, a butterfly-shaped organ in the front part of the neck that produces thyroid hormone, is very common. These growths, called nodules, frequently develop in both sides of the gland (in both ‘wings’ of the butterfly-shaped thyroid). Most of the time, thyroid nodules are benign (non-cancerous), although a small fraction will turn out to be cancerous. The most common type of thyroid cancer is called papillary thyroid cancer and this type of cancer has an excellent prognosis. Treatment for papillary thyroid cancer usually requires thyroid surgery, which may involve removing only that part of the thyroid in which the cancer is discovered (called a thyroid lobectomy) or removing the entire thyroid gland (called a total thyroidectomy).

A thyroid lobectomy has several advantages compared to total thyroidectomy. First, the non-cancerous portion of the thyroid that is not removed (the other ‘wing’ of the butterfly-shaped thyroid) will continue to make thyroid hormone, often enough to avoid needing to take a thyroid hormone replacement pill after surgery. In contrast, a person who has a total thyroidectomy will not have any thyroid tissue left to make thyroid hormone after surgery and will have to take a thyroid hormone pill each day, for the rest of their life. Second, the risks related to undergoing thyroid surgery, in particular voice hoarseness and permanently low body levels of calcium, are lower for thyroid lobectomy than for total thyroidectomy.

A major disadvantage of thyroid lobectomy, compared to total thyroidectomy, however, is that the remaining thyroid not removed during surgery may also contain or, at some point may form, another papillary thyroid cancer, especially if nodules are already present in this remaining thyroid tissue. The authors of the research described here sought to study the risk of papillary thyroid cancer being present, or developing over time, for people who underwent thyroid lobectomy for treatment of papillary thyroid cancer and for whom nodules were known to be present in that thyroid tissue not removed during surgery.

THE FULL ARTICLE TITLE
Pak SJ et al Contralateral low-to-intermediate suspicion nodule is not a contraindication for lobectomy in patients with papillary thyroid carcinoma. Thyroid. Epub 2023 Aug 25. PMID: 37624735

SUMMARY OF THE STUDY
The authors of this work reviewed the medical records for everyone who had a thyroid lobectomy for treatment of papillary thyroid cancer at their institution between January 2016 and December 2017. This included 1761 people, 700 of whom were known to have at least one nodule in that part of the thyroid not removed during surgery. Over time, 54% of these nodules stayed the same, became smaller or disappeared altogether. These findings are reassuring, as cancerous nodules tend to grow. On the other hand, 14.8% of nodules grew over time, which raises concern for the presence of thyroid cancer. Overall, 20 of the 700 people (2.9%) having nodules in the thyroid tissue not removed during thyroid lobectomy were ultimately found to have papillary thyroid cancer in this remaining thyroid tissue. However, the 5-year survival rate (which was excellent at 98.7%) was the same for people having known nodules in the thyroid tissue not removed during thyroid lobectomy compared to people without such nodules. The authors did find that having nodules in the thyroid tissue not removed during thyroid lobectomy was associated with higher risk of this cancer in the remaining thyroid tissue, especially if ultrasound of these nodules showed features suspicious for thyroid cancer. The authors also found that these nodules tended to grow over time, especially if they were bigger than 1 cm in diameter at the time of thyroid lobectomy.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This work shows that for people diagnosed with papillary thyroid cancer who are candidates for thyroid lobectomy, but who also have known nodules in the thyroid tissue that would be left behind after this surgery, thyroid lobectomy is a reasonable treatment choice. This is especially true if ultrasound of these nodules does not show any features suspicious for cancer. These findings are encouraging, as thyroid lobectomy may allow a person to avoid the need to take a thyroid hormone replacement pill after surgery and has lower risks of complications during surgery compared to total thyroidectomy. This being said, this study also indicates that nodules in the thyroid not removed during thyroid lobectomy should be monitored over time, as a small number of these will be cancerous and will need to be treated with additional surgery.

— Jason D. Prescott, MD PhD

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