medwireNews: Earlier age at diagnosis of childhood differentiated thyroid cancer (DTC) is associated with a greater risk of advanced disease, but overall, patients have excellent long-term survival irrespective of age, stage, and treatment response, US study findings indicate.
However, some paediatric patients “may experience disease progression later in life, suggesting that long-term follow-up might be appropriate for this population,” write Matthew Ringel and colleagues from The Ohio State University College of Medicine and Arthur G James Comprehensive Cancer Center in Columbus, in The Journal of Clinical Endocrinology & Metabolism.
They reviewed data for 155 people diagnosed with DTC between 9–20 years of age (median age 17 years; 82.6% girls), of whom 20.0% were diagnosed before age 15 years. Among the entire cohort, 92.3% had papillary thyroid cancer and 7.7% had follicular thyroid cancer.
The researchers report that, at diagnosis, tumour stage was T1 in 32.9%, T2 in 27.1%, T3 in 27.1%, and T4 in 7.1%, and most (63.9%) had lymph node involvement. The majority (79.4%) of participants had stage I disease and 17.4% had stage II disease with distant metastases, with the stage unknown in the remainder of the patients.
In terms of treatment, three-quarters (75.5%) of patients underwent total thyroidectomy as their initial surgery, while the remainder had partial surgeries with (21.9%) or without (1.9%) completion. Just over half (56.8%) of patients were given one dose of radioactive iodine (RAI), 20.0% had two doses, 12.9% had three or more doses, and 10.3% were not given RAI. The median cumulative RAI dose was 150 mCi.
Ringel and team found that, after a median 16 years (range 1–63 years) of follow-up, 52.3% of patients had an excellent response according to American Thyroid Association guidelines and none had died because of DTC. A quarter (25.2%) had an indeterminate response, 18.7% had a structurally incomplete response and 3.9% had a biochemically incomplete response. During follow-up, two patients received targeted therapies for thyroid cancer.
Multivariate analyses with age as a continuous variable showed that younger patients were significantly more likely to have larger, more invasive tumours, and distant metastases at diagnosis than older patients, meaning that there was a significant inverse correlation between age and overall stage at diagnosis.
Younger age at diagnosis also correlated with worse response at last follow-up. Indeed, each 1-year increase in age at diagnosis was associated with a significant 22% lower likelihood of having an indeterminate or incomplete response.
The researchers also note that patients with stage II DTC at diagnosis, were 5.8 times more likely to be in a worse response category at last follow-up than patients with stage I DTC, which they say suggests that “when they occur, distant metastases are controlled but not often cured.”
A subgroup analysis of nine patients with stage I or II disease and over 50 years of follow-up showed that these patients had median of 36 years of disease stability, but progression eventually occurred and needed intervention in two-thirds of them.
“This decades-long follow-up information is overall reassuring to families facing a pediatric DTC diagnosis while also suggesting that long-term follow-up might be appropriate for adults with a history of pediatric thyroid cancer to monitor for disease progression events later in life,” Ringle et al conclude.
By Laura Cowen
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