Radioactive iodine (RAI) may be selectively used for the treatment of intermediate-risk papillary thyroid cancer in patients who are aged over 45 years with tumors smaller than 4 cm that are confined to the thyroid gland, say US scientists.
Ian Ganly (Memorial Sloan-Kettering Cancer Center, New York) and colleagues suggest: "Our data can be used to identify patients who can be safely treated without RAI.
"These patients are older than 45 years with T1 and T2 tumors and without any adverse histologic features or pathologically positive neck disease."
They add: "All other intermediate-risk patients should be treated with adjuvant RAI with the exception of a few highly selected young patients with limited neck disease in both the number and the size of affected nodes."
The researchers studied 532 patients at intermediate risk of death from papillary thyroid cancer surgically treated with total thyroidectomy between 1986 and 2005. Of these patients, 307 also underwent RAI, the team reports in the Archives of Otolaryngology - Head & Neck Surgery.
Of the 344 patients aged over 45 years, 57% did not receive RAI. These patients were more likely to be female, have pT1 disease, and be free of nodal metastases. In addition, 91% of patients in this group were deemed to be at low risk of recurrence.
Over a median follow up of 51 months, 5-year disease-specific survival (DSS) and recurrence-free survival (RFS) were 100% and 97%, respectively. Five-year RFS in the RAI and no-RAI groups were 96% and 98%, respectively.
In patients aged over 45 years, positive nodal status was a significant predictor of recurrence, with 5-year RFS of 99% for N1 versus 91% for N0 disease. There was no significant difference in DSS or RFS between patients who did or did not receive RAI.
Of the 188 patients younger than 45 with high-risk tumors, only 15% were treated without postoperative RAI. Over a median follow up of 54 months, the 5-year DSS and RFS were 100% and 95%, respectively. For the RAI and no-RAI groups, 5-year RFS was 88% and 95%, respectively. Nodal status was the only significant predictor of poor outcome, at a 5-year RFS of 100% for patients with no nodal metastases versus 86% for those with nodal metastases.
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