Role Of Adjuvant Radioactive Iodine Questioned For Recurrent Papillary Thyroid Cancer

Radioactive iodine ablation after reoperation of recurrent or persistent papillary thyroid cancer may not improve outcomes

medwireNews: The biochemical and oncological outcomes of patients who undergo reoperation for recurrent or persistent papillary thyroid cancer appear to be comparable regardless of whether they receive radioactive iodine after surgery, indicates a chart review in JAMA Surgery.

Michael Yeh and co-researchers, from the University of California, Los Angeles in the USA, explain that “[a]lthough the long-term prognosis for patients with [papillary thyroid cancer] is excellent, up to 30% of patients experience persistent or recurrent locoregional disease after initial treatment”, for which the American Thyroid Association recommends reoperation.

To clarify the role of radioactive iodine ablation after surgery, they identified 102 patients with persistent or recurrent papillary thyroid cancer who had a reoperation at a US tertiary referral centre; 50 of them received radioactive iodine, while the remaining 52 did not.

Within 6 months of reoperation, 12% of 33 evaluable patients treated with radioactive iodine had an excellent response, defined as the absence of clinical, biochemical or structural evidence of disease and thyroglobulin levels below 0.2 ng/mL.

By contrast, the rate of excellent response was 47% for the 51 evaluable participants who did not receive radioactive iodine, a significant difference.

Moreover, patients in the radioactive iodine group were more likely to experience structural recurrence after reoperation than those in the control group, with rates of 36% and 19%, respectively.

But there was no significant difference between the groups in terms of recurrence-free survival following reoperation.

In light of these findings, the investigators comment that the receipt of radioactive iodine after surgery “was not associated with a significant clinical benefit in this limited series.”

However, they urge caution in interpreting the results, as patients who received radioactive iodine “may have had more aggressive disease” than those who did not, as indicated, for instance, by the higher proportion of T3 and T4 tumours at initial surgery (56 vs 37%), and “may have been preferentially selected to receive [radioactive iodine] after reoperation.”

The team continues: “In that case, patients in the reoperation with [radioactive iodine] group would be expected to have worse outcomes, which could obscure a potential therapeutic benefit of [radioactive iodine].

That said, a multivariate analysis adjusting for disease burden and tumour stage also failed to show a significant association between radioactive iodine treatment and a reduction in the risk of second recurrence.

Nonetheless, Michael Yeh and colleagues call for larger multicentre studies “to determine whether receipt of radioactive iodine after operation improves outcomes among patients with recurrent papillary thyroid cancer.”

Reference

Hung ML, Wu JX, Li N, Livhits MJ, Yeh M.W. Association of radioactive iodine administration after reoperation with outcomes among patients with recurrent or persistent papillary thyroid cancer . JAMA Surg; Advance online publication 15 August 2018. doi: 10.1001/jamasurg.2018.2659

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