From 2000 to 2018, use of radioactive iodine therapy in papillary thyroid cancer treatment greatly declined in favor of total thyroidectomy alone without radioactive iodine or lobectomy, according to study data.

Cari M. Kitahara

“Since we now know that many low-risk thyroid cancers can be managed effectively with less aggressive approaches, often with the same or better outcomes, the American Thyroid Association guidelines strongly recommend less or no radioactive iodine and lobectomy instead of total thyroidectomy for thyroid cancers without aggressive features,” Cari M. Kitahara, PhD, senior investigator in the division of cancer epidemiology and genetics at the National Cancer Institute, told Healio. “For the first time, the 2015 guidelines listed active surveillance as a viable option for some very low-risk thyroid cancers. Our results showed that physicians have been quick to adapt to these changing practice guidelines. In particular, we saw a clear shift away from radioactive iodine therapy for smaller papillary thyroid cancers.”

Kitahara and colleagues analyzed data from 18 Surveillance, Epidemiology and End Results (SEER) cancer registries. People diagnosed with primary papillary thyroid cancer between 2000 and 2018 were included in the analysis. The cohort was classified by treatment type: total thyroidectomy followed by radioactive iodine, total thyroidectomy alone, lobectomy, no surgery or other/unknow therapy. Trends by tumor size were analyzed, and for those with a tumor smaller than 4 cm, cases were stratified by age, sex, race and ethnicity, the patient’s residence at diagnosis and insurance status.

The findings were published in Thyroid.

There were 105,483 patients diagnosed with papillary thyroid cancer during the study period, with 98% having a tumor of less than 4 cm and 50% having a tumor of less than 1 cm.

For those with a tumor smaller than 4 cm, the use of radioactive iodine after a total thyroidectomy increased from 35% in 2000 to 38% in 2006 before dropping to 18% in 2018. The percentage of participants having a total thyroidectomy alone increased from 35% in 2000 to 54% in 2018. Lobectomy increased from 17% in 2015 to 24% in 2018. No measurable changes in treatment were observed for those with a tumor 4 cm or larger.

Kitahara said it was surprising to see lobectomy use increase only slightly with the changes in ATA recommendations. Additionally, the use of nonsurgical management remained at less than 1% during the entire study period.

“There may be some hesitation on behalf of both physicians and patients to use less aggressive therapeutic approaches,” Kitahara said. “Some physicians may not be convinced of their overall safety and waiting for more evidence, and some patients may prefer more aggressive therapies because they are worried about recurrence or metastasis. Also, active surveillance is a fairly new approach in thyroid cancer management, and so it may take some time before we see more widespread acceptance. There are still some practical issues with active surveillance, including uncertainty about the cost-effectiveness, and the need for long-term monitoring.”

Before 2010, radioactive iodine after total thyroidectomy was more common for younger people than older adults, peaking at 60% in 2009 for adolescents younger than 20 years. By 2018, radioactive iodine use was below 20% in all age groups and lowest for adolescents at 11%. Radioactive iodine use was highest among Asians/Pacific Islanders and Hispanic patients and lowest for non-Hispanic Black patients.

With the ATA developing another update to its thyroid cancer treatment guidelines, it will be important to continue monitoring trends to see what impact on clinical practice the updates will have, Kitahara said.

“More research is also needed to understand reasons for departures from the treatment guidelines, including physician and patient preferences and other barriers to less aggressive therapeutic options,” Kitahara said.