medwireNews: Radioactive iodine (RAI) therapy may be avoided for some children undergoing surgery for papillary thyroid carcinoma (PTC), suggest findings from a study that shows good outcomes even for those with cervical lymph node metastases.
“[W]ithholding therapeutic RAI within one year of diagnosis does not appear to result in higher rates of persistent/recurrent disease compared with historical studies”, say Steven Waguespack (The University of Texas MD Anderson Cancer Center, Houston, USA) and co-authors in the Journal of Clinical Endocrinology & Metabolism.
They explain that while considered “generally safe”, RAI is associated with “acute and chronic side effects and long-term risks such as second primary malignancies, especially leukemia and solid tumors, risks that may take decades to manifest.”
Recognising that adult guidelines do not recommend RAI for low-risk patients, the team conducted an ambispective study using information for 93 patients younger than 19 years old who were diagnosed with PTC and treated at a tertiary centre between 1990 and 2021.
The patients were aged a median of 16 years at diagnosis, 87% were girls, and 58% were White, while 27% were Hispanic/Latino, 11% Asian and 4% Black.
The primary tumour size was a median 18 mm and most (65%) patients had stage I disease, 25% had stage 2 and 6% had stage 3, while almost half (49%) had cervical lymph node metastases. The majority (65%) of patients had a low American Thyroid Association risk status, 25% had an intermediate risk and 10% a high risk. Underlying molecular drivers were unknown in 69% of patients but 27% had a BRAF V600E mutation and 2% each had a RET or NTRK3 fusion alteration.
The majority (75%) of patients underwent total thyroidectomy with or without neck dissection, 21% had lobectomy with or without neck dissection and 4% underwent a Sistrunk procedure for ectopic PTC.
RAI was withheld from 48% of patients because of “favorable pathology after total/two-stage thyroidectomy”, from 22% because they required only lobectomy, and from 20% because of an “excellent response on [dynamic risk stratification]”, the researchers explain. The rest of the patients did not undergo RAI because of stem cell transplantation for leukaemia, cancer predisposition syndrome or other reasons.
Overall, 95% of patients were considered free from disease after their initial surgery and 5% had persistent disease, report Waguespack et al.
Moreover, 91% of patients were free from disease and required no further treatment after a median 5.5 years of follow-up, and this included all four of the patients who were younger than 10 years old at the time of diagnosis.
Of the five patients with persistent disease, two had stable disease for 5 and 10 years without further treatment. The third patient had stable central neck disease despite undergoing completion thyroidectomy with neck dissection and RAI 6 years after diagnosis, followed by a third procedure. The fourth patient had progressive structural disease in a previously unoperated compartment and further surgery was planned. The fifth patient underwent initial Sistrunk procedure for a large cystic mass and was subsequently found to have PTC requiring total thyroidectomy and cervical neck dissection, followed by RAI and has had an “excellent response” 6 years on, the authors say.
Three patients who were considered cancer-free subsequently experienced recurrence after 4, 5 and 15 years of follow-up; one patient was disease-free after further surgery and RAI, one patient underwent completion thyroidectomy and became disease-free, and a third had biochemical recurrence and lung metastases that did not respond to RAI.
The researchers highlight that 80% of the 20 patients who initially underwent lobectomy and were followed-up for a median 3 years had an “excellent response”, while two had an “indeterminate response” and one had an “excellent response” after completion thyroidectomy for recurrence.
They summarise that the study’s 9% rate of PTC persistent or recurrence “was lower than published recurrence rates of 14–40% in children with [differentiated] TC suggesting that withholding RAI is a non-inferior approach for selected patients such as those included in the current study.”
Waguespack and co-authors therefore conclude: “This approach warrants further investigation in the context of larger studies with longer follow-up.”
By Lynda Williams
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