Study Supports Selective RAI Use in Papillary Thyroid Cancer

Marlene Busko

June 28, 2013

Carefully chosen patients with papillary thyroid cancer who had total thyroidectomies without subsequent radioactive iodine remnant ablation (RRA) have excellent disease-free survival, researchers report.

The work by Iain Nixon, MD, from the Memorial Sloan-Kettering Cancer Center (MSKCC) in New York, and colleagues was first presented at the American Thyroid Association (ATA) annual meeting last year and is now published in the June issue of Thyroid.

In certain patients, the benefits of radioactive iodine treatment may outweigh potential harm, but this "is not [as harmless as] a vitamin pill" and "should be used very judiciously," senior author Jatin P. Shah, MD, from MSKCC, told Medscape Medical News.

In their retrospective analysis of more than 1000 patients who underwent total thyroidectomies at their center, most patients with low-risk local disease and even some patients with high-risk, T3 tumors who did not receive RRA after surgery had high 5-year recurrence-free survival rates.

Their findings confirm that postsurgery RRA "is clearly not indicated" for low-risk patients, which agrees with the American Thyroid Association guidelines, Dr. Shah noted. On the other hand, RRA "should be employed…[for high-risk patients], because anything that has any potential benefit should be employed, [including radioactive iodine and] experimental new drugs," he added. Finally, for patients at intermediate risk, "clinicians should use their discretion to select who should or should not get radioactive iodine [treatment], based on the nature [and extent] of the tumor…and the surgery," he advised.

Forgoing vs Undergoing RRA

In the past, RRA was widely used after thyroid surgery to "mop up" any remnant thyroid tissue, because it was perceived to be harmless. "But that is not quite true," Dr. Shah explained, since radioactive iodine "will certainly produce dryness in the mouth, recurrent or frequent episodes of [inflamed, tender, and swollen] salivary glands — a lifelong risk — and now we know it increases the risk of [more serious] secondary cancer [such as colon and breast cancer] in as many as 12% of patients."

To investigate this, he and his colleagues looked at just over 1000 consecutive patients who had total thyroidectomies at the MSKCC between 1986 and 2005. The patients had a median age of 46 years and there were almost 3 times as many women as men.

The study included:

  • 490 low-risk patients who had primary disease that was limited to the thyroid gland (pT1–2 N0)

  • 193 intermediate-risk patients with primary disease and evidence of regional metastases (pT1–2 N1)

  • 444 high-risk patients with advanced (pT3 or T4) local tumors

All patients had extracapsular thyroidectomy and therapeutic neck dissection to remove proven or suspicious cervical lymph-node metastases, and 691 patients (61%) received RRA.

During a mean follow-up of 5 years, 18 patients (2%) died of thyroid cancer, and 84 patients (7%) had a recurrence.

Patients over the age of 45 years were 8.9 times more likely to die of the disease than younger patients, and patients with stage T4 disease were 5.5 times more likely to die than patients with stage T1 cancer.

The 5-year disease-specific survival and recurrence-free survival rates were 99% and 92%, respectively, for the group.

Careful Patient Selection Is Key

In the low-risk group, more than half of patients (64%) did not receive adjuvant radioactive iodine, with no detrimental impact on 5-year survival rates.

In the intermediate-risk group, 26% of the patients were carefully selected not to have RRA, with no negative impact on these outcomes.

The study confirmed that "a highly selected group of young patients with pT1–2 tumors, fewer than 5 positive nodes, and with microscopic deposits of cancer may be managed with observation without RRA and with careful monitoring of thyroglobulin levels and regular ultrasound," the authors write.

In the high-risk group, 16% of patients, mainly those with T3 disease and no cancer in the cervical lymph nodes, were carefully selected to not receive RRA, and again, this treatment strategy had no detrimental impact on 5-year survival or recurrence.

"Nearly 80% of thyroid-cancer patients fall in the low-risk category" and do not need radioactive iodine treatment after all the thyroid tissue has been removed, Dr. Shah summarized, adding that the surgeons in this study were highly experienced.

The guidelines have changed from 2006 to 2009, and as more studies like this one are being published, he expects that indications for RAI following total thyroidectomy will continue to decline.

The authors call for individualized treatment, nevertheless. "The results of this study should not lead clinicians to reject the use of RRA in lower-risk patients," they caution. "However, a balance between risk and benefit must be made on an individual patient basis."

The authors have reported no relevant financial relationships.

Thyroid. 2013;23:683-694.

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