BACKGROUND
Thyroid cancer is common and papillary thyroid cancer is the most common type of thyroid cancer. Papillary thyroid cancer has an excellent prognosis, particularly in patients <55 years of age. As such, papillary thyroid cancer is usually classified according to the risk of the cancer returning after initial treatment rather than the likelihood of dying of the cancer. This risk is rated as low, intermediate and high. Since the vast majority (>90%) of patients with papillary thyroid cancer, especially those with low and intermediate risk, do not die of their cancer, it can be difficult to evaluate the effect of treatment on overall survival in patients with low to intermediate risk papillary thyroid cancer. For example, while most studies show little effect of the presence of the spread of the cancer to lymph nodes in the neck on overall survival, their presence does increase both persistence and recurrence of the cancer.

Spread of the cancer to lymph nodes in the neck is common in papillary thyroid cancer, ranging from a low of 20% of patients to up to 90% of patients when neck dissections are performed as part of initial surgery. When spread of the cancer to lymph nodes in the neck is discovered during the initial surgery, radioactive iodine therapy is usually recommended.

This study was performed to evaluate whether the use of radioactive iodine therapy can improve survival in patients with low-to-intermediate risk papillary thyroid cancer that have spread of the cancer to lymph nodes in the neck at the time of surgery.

THE FULL ARTICLE TITLE
Palacardo F, et al. The impact of radioactive iodine on disease-specific survival in low-to-intermediate risk N1b papillary thyroid carcinoma. Ann Surg Oncol. Epub 2024 Nov 6; doi: 10.1245/s10434-024-16388-1. PMID: 39505729.

SUMMARY OF THE STUDY
The authors used a major database (SEER) to identify patients ≥18 years, diagnosed with papillary thyroid cancer from 2004-2015 who underwent total thyroidectomy with any lymph nodes resected during the initial operation. The average follow up was 7.5 years. They looked at predictors of survival such as age, sex, cancer size, race, risk, lymph node involvement and cancer extension outside the thyroid. Patients ≥55 years were analyzed separately. A total of 4601 adults were evaluated, of whom 78.6% received radioactive iodine therapy and 21.4% did not.

While overall there was improvement in survival with radioactive iodine therapy, on subgroup analysis it was only seen in patients ≥55 years and not seen in the group of younger patients. Other factors in the ≥55 group associated with worse survival were larger cancer size and any invasion into or beyond the thyroid capsule. The only factor associated with improved outcome in the younger group was female sex with improved survival.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study suggests that radioactive iodine therapy is associated with improved survival in patients with intermediate- risk papillary thyroid cancer and age ≥ 55 years, but not in patients with otherwise low-risk features. This information can help to limit radioactive iodine therapy treatment to those who are more likely to benefit from it and avoid potential side effects when radioactive iodine therapy may not be helpful.

— Marjorie Safran, MD

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