Omitting Adjuvant Radioactive Iodine for Select Patients With Pediatric Papillary Thyroid Carcinoma
Luz Castellanos, MD, MD Anderson Cancer Center, Houston, Texas, shares results from an ambispectric trial evaluating outcomes of patients with pediatric papillary thyroid carcinoma who did not receive adjuvant radioactive iodine.
Dr Castellanos concluded, “Historically, radioactive iodine was almost a reflexive next step, but now we're realizing that many kids simply don't need it, and the approach should be individualized.”
Transcript:
Hello. I'm a board-certified pediatric endocrinologist and assistant professor in the department of endocrine, neoplasia and hormonal disorders at MD Anderson Cancer Center. And I'm going to be talking about our publication, “Pediatric papillary thyroid carcinoma and outcomes after surgery without adjuvant radioactive iodine.”
Over the last 2 decades, pediatric papillary thyroid cancer has been on the rise, and children do often present with more advanced disease compared to adults, including nodal and distant metastasis. Despite that, long-term survival is outstanding and very few deaths are related to pediatric papillary thyroid cancer. Historically, every child diagnosed with papillary thyroid cancer received radioactive iodine after a total thyroidectomy. This has been a longstanding practice really aimed at reducing recurrence. But, there's been a lack of high-quality evidence guiding the role of radioactive iodine in kids. In 2015, the American Thyroid Association did publish the pediatric thyroid cancer guidelines for the first time, and there was consideration of a more selective approach to radioactive iodine in pediatric patients with the goal of not just preventing recurrence but also minimizing harm from treatment.
Although radioactive iodine is generally considered safe, we now recognize potential risks, particularly in younger patients, including sialadenitis, ocular dryness, bone marrow suppression, xerostomia, dental caries, gonadal damage. And there's concern for potential long-term effects with repeated dosing especially. This really requires decades of follow-up to fully understand, but there's concerns for gonadal damage and increased risk of second primary malignancies. Experts are becoming increasingly more aware that not all patients benefit from radioactive iodine treatments, and there's multiple limitations to its effectiveness. This is reflected in the dramatic decrease in radioactive iodine administration. The question is, if radioactive iodine isn't truly effective in all pediatric patients, are we exposing these children to unnecessary risks? We asked this question for our study.
This was a retrospective cohort study conducted at MD Anderson Center, spanning over 3 decades from 1990 to 2021, looking at pediatric patients less than 19 years of age, who had stage 1 papillary thyroid cancer at diagnosis, meaning they had no distant metastases. They had no radioactive iodine within that first year of diagnosis, and at least 1 year of follow-up. Our co-primary outcomes were looking at disease status at that last follow-up, and the proportion of patients remaining cancer-free. Let’s break down the results of the study. We did review 93 pediatric patients treated surgically for papillary thyroid cancer between 1990 and 2021, a total of three quarters had a thyroidectomy and about one quarter had a lobectomy. Postoperatively, we do stage all these patients, and we also assess their risk of recurrence. Two thirds were considered low risk and one third were considered intermediate or high risk. And we also wanted to understand the reasons why radioactive iodine was not given to this population. The majority, over 40%, was due to low-risk disease and followed by a quarter of patients who had no evidence of disease, followed by a lobectomy, or a combination of other similar reasons if they had ectopic tumor or cancer predisposition syndromes.
And the key finding from this population is that after a median follow-up of over 5 years, the vast majority, over 90%, were disease-free after surgery alone, without needing additional therapy, which does suggest that in many cases, skipping the radioactive iodine did not compromise outcomes. And this really does align with what we've been seeing in adult low-risk thyroid cancer cases where surgery alone can be enough, but pediatric thyroid cancer does have some unique characteristics like higher prevalence of lymph node involvement. And despite that, nearly half of the patients in the study had nodal disease and most still did well without their radioactive iodine.
I also want to talk about the 9% of patients who had either persistent or recurrent disease. And interestingly, 4 of these patients eventually did receive radioactive iodine, but only 1 had excellent response to this treatment. And meanwhile, 2 patients who underwent additional surgery alone had excellent outcomes, which does raise questions about the role of surgery versus radioactive iodine in these cases. And another interesting takeaway is that in some of these cases, even when there is persistent disease, it really remains stable over time, suggesting that active surveillance can be viable for select patients. And another group of the study we looked at was those treated with lobectomy alone. And this is something we've been seeing for smaller and lower risk tumors. And here about 80% had excellent outcomes without additional treatment, and there was 1 case of recurrence that was 16 years later that really emphasizes the need for long-term follow-up.
This study does really reinforce the idea that we don't need a one-size-fits-all approach to pediatric thyroid cancer, and this aligns with the shift in how we've been treating these patients. Historically, radioactive iodine was almost a reflexive next step, but now we're realizing that many kids simply don't need it, and the approach should be individualized. This study does challenge that longstanding management of giving radioactive iodine. We’re showing that some children, and this is particularly in stage 1, who have low risk and no evidence of disease, despite having nodal involvement, can have excellent outcomes without radioactive iodine.
Source:
Castellanos LE, Zafereo ME, Sturgis EM, et al. Pediatric papillary thyroid carcinoma: outcomes after surgery without adjuvant radioactive iodine. JCEM. Published online August 20, 2024. doi:10.1210/clinem/dgae576
