Recurrence uncommon for adults with medullary thyroid microcarcinoma
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Key takeaways:
- Most adults with medullary thyroid microcarcinoma do not experience disease recurrence or cancer-related death.
- Pathological grading can identify those at risk for worse outcomes.
In a small group of adults diagnosed with medullary thyroid microcarcinoma, few had disease recurrence or died during more than 6 years of follow-up, according to findings from an Australian database.
“Patients with sporadic medullary thyroid microcarcinoma generally have good outcomes, with most cancers being detected incidentally and that, if low grade with a normal postoperative calcitonin, these are not associated with structural recurrence,” Nicholas L. Kesby, a medical student in the endocrine surgery unit at Royal North Shore Hospital in Sydney and in the faculty of medicine at University of New South Wales, and colleagues wrote in a study published in The Journal of Clinical Endocrinology & Metabolism. “In this study, a high-grade cancer, lymph node metastasis and a raised postoperative calcitonin were associated with structural recurrence. As grade is available at the time of pathological review, the use of this system offers the opportunity to tailor follow-up and further treatment to higher-risk patients.”
Researchers analyzed data from an endocrine surgery database at a tertiary referral center in Australia. Adults treated for medullary thyroid carcinoma between 1995 and 2022 who did not have hereditary disease and whose largest tumor was 10 mm or less in size were included. Demographics, operative details, tumor pathology, follow-up details, biochemistry and imaging were collected from the database. Tumors were graded using a system approved by WHO and the International Agency for Research on Cancer. The primary endpoints were the percentage of adults with disease recurrence, the time to recurrence and disease-specific survival.
There were 42 adults included in the study (67% women; median age, 60 years), of whom 86% were diagnosed with incidental medullary thyroid microcarcinoma after surgery for another condition. Of the cohort, 27% underwent a hemithyroidectomy, with the remaining adults having a total thyroidectomy. A central lymph node dissection was performed in 38% of adults at the time of operation.
Median medullary thyroid microcarcinoma size was 4 mm. No adults had distant metastatic disease at the time of presentation. There were 14 adults with multifocal cancers, of whom 12 had simultaneous papillary thyroid cancer. Most of the adults with papillary thyroid cancers had larger tumors than what was observed in their medullary thyroid microcarcinoma.
Tumor grading was performed for 41 adults. Of those with grades available, 37 had low-grade cancer and four had high-grade cancer. Of 40 adults with at least one calcitonin result available, eight had a raised level, with a median postoperative calcitonin of 5 ng/mL.
During a median follow-up of 6.6 years, five adults had cancer recurrence, of whom three had initial recurrence with local lymph node disease in the neck, one had distant disease and one had both local and distant disease. There were 11 deaths, of which three deaths were due to medullary thyroid microcarcinoma. The three adults who died developed multi-organ distant metastasis 4 to 8 years after their initial diagnosis.
The 5-year estimate of being free of recurrence was 90.5%, 5-year disease-specific survival was 100% and 5-year overall survival was 84.3%. Adults with low-grade microcarcinoma had a better 5-year estimate for time to recurrence than those with high-grade disease. The median time to recurrence for high-grade cancers was 6.25 years. Adults with high calcitonin levels were more likely to have structural recurrence than those with normal calcitonin. There were no differences in recurrence by surgical approach. Adults who presented with medullary thyroid microcarcinoma were less likely to have stage 1 disease (50% vs. 94%), more likely to have lymph node metastasis (50% vs. 6%) and had higher rates of recurrence and worse survival than people with an incidental diagnosis.
“The use of grading in medullary thyroid microcarcinoma warrants further research as it represents a potential tool to assist in determining the appropriate extent of surgery and follow-up following the identification of sporadic medullary thyroid microcarcinoma,” the researchers wrote.
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