Blanket Approach to RAI in PTC Patients May Not Be Necessary

Scrape cytology illustrating features of papillary carcinoma of the thyroid.

A blanket approach to the use of radioactive iodine (RAI) may not be necessary in many patients with papillary thyroid cancer (PTC) provided they undergo expert total thyroidectomy first, Memorial Sloan-Kettering Cancer Center (MSKCC) investigators have shown. Findings were presented at the annual meeting of the American Thyroid Association (ATA).

Iain Nixon, MD, and MSKCC colleagues retrospectively reviewed outcomes for 1129 PTC patients who had undergone total extracapsular thyroidectomy between 1986 and 2005. As Nixon emphasized, there was no evidence of macroscopic residual disease following surgery, and it was assumed patients were disease-free at the time of risk stratification.

The median age of the cohort was 46 years; 39% overall had T3/T4 disease and more than 40% had nodal disease. “Overall, these patients did well,” Nixon observed, “as disease-specific mortality was only 1% and our recurrence rate at 5 years was 8%.” They subsequently analyzed a subgroup of 490 patients whose disease was confined to the thyroid, approximately two-thirds of whom were selected not to receive RAI.

“At a median follow-up of 63 months, select patients with early primary disease (pT1/T2) and low-volume metastatic disease in the neck (pT1/T2 N1) managed without RAI had excellent outcomes,” investigators report. None of the patients died during follow-up, as Nixon noted. At 5 years, regional and distant recurrence rates of only 2% and 1%, respectively, were not statistically different between those selected not to undergo RAI and those who did, he added.

Another 193 patients had limited local disease but with evidence of nodal metastasis, approximately one-quarter of whom were selected not to receive RAI. Again, those selected not to receive RAI had “excellent outcomes,” as Nixon noted, with virtually no local or distal recurrences observed over the 5 years of follow-up.

The majority of another group of 444 patients with more aggressive local disease—T3/T4—did receive RAI. Of the 16% who did not, there were again no deaths at 5 years. At 2% and 7% for regional and distant recurrence rates respectively, outcomes were again very acceptable, as Nixon suggested.

“I should make it clear that in our institution we still use RAI in low, intermediate, and high-risk groups on an individually selective basis,” Nixon said. “But we know treatment is not without side effects in terms of salivary and lacrimal dysfunction and increased rates of dysphagia, and there is a risk of secondary malignancy as well. Our findings suggest that most patients whose disease is limited to the thyroid and even selected patients with low-risk, local disease and limited nodal disease have good outcomes following management without RAI.”

ATA guidelines on the management of well-differentiated thyroid cancer currently recommend the routine use of radioactive iodine for the treatment of tumors >4 cm and selective use of radioactive iodine in patients with intrathyroidal disease that is <1 cm. RAI is also recommended for patients who have evidence of nodal metastases.

The guidelines acknowledge, however, that data upon which to make firm recommendations for most patients are both conflicting and inadequate.

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