Latest ATA Guidelines Best Predict Thyroid Cancer Recurrence

Miriam E Tucker

February 10, 2017

The American Thyroid Association's 2015 "response to therapy restratification" (RTR) may be the most accurate predictor of risk of recurrence in papillary thyroid cancer, new research from South Korea suggests.

The findings were published in the February issue of Thyroid by Seul Gi Lee, MD, of Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Korea, and colleagues.

The 2015 American Thyroid Association (ATA) management guidelines indicate the initial risk of structural disease recurrence based on clinicopathologic features for patients without structurally identifiable disease after initial therapy (ATA 2015 initial risk stratification [RSS]) and also suggest that clinicians use the RTR in the new guidelines to estimate the risk of recurrence (ATA 2015 RTR).

From retrospective data for 2425 papillary thyroid cancer patients who underwent thyroidectomy at their institution, Dr Lee and colleagues compared the predictive accuracy of the two 2015 risk-stratification systems (ATA 2015 RSS and ATA 2015 RTR) with that of the prior 2009 ATA management guidelines (ATA 2009 RSS).

The results, they say, show that "all three risk-stratification systems that were examined are useful for predicting the risk of recurrence after initial treatment, although the ATA 2015 RTR was the most accurate," despite the fact that the data do not include BRAFV600E and TERT promoter mutation status, and the mean follow-up period was relatively short (88 months).

Some Patients Shifted Risk Categories

The study patients (mean age 45 years, 86.5% female) had all undergone total thyroidectomy with central neck node dissection with or without modified radical neck node dissection between October 1985 and July 2009. Using the ATA 2009 RSS, 15.5% were classified as low risk, 78.9% as intermediate, and 5.6% as high risk.

When the ATA 2015 RSS was applied, 13.5% of those originally designated as intermediate risk by the 2009 system were redesignated as low risk. This was primarily because the number of metastatic lymph nodes was low, Dr Lee and colleagues point out.

At the same time, five patients initially placed in the intermediate-risk group with the 2009 criteria shifted to the 2015 high-risk group due to the larger size of the metastatic lymph nodes.

Overall, using ATA 2015 RSS, the proportion of patients in the low-, intermediate-, and high-risk groups were 26.1%, 68.0%, and 5.9%, respectively.

Predicting Recurrence

Recurrence was detected in 136 (5.6%) patients during follow-up.

On the one hand, all three systems predicted tumor recurrence well. The ATA 2015 RTR categorized 65% of all patients into the ''excellent-response'' group, with a low rate of recurrence (1.1%), similar to the 1.1% and 0.9% rates predicted by the ATA 2009 RSS and ATA 2015 RSS, respectively.

However, because the ATA 2009 RSS classified 15.5% of patients as low risk and the ATA 2015 RSS classified 26.1% as low risk, "the ATA 2015 RTR might be a better and more cost-effective predictor of tumor recurrence…although it cannot be used at the preoperative stage," Dr Lee and colleagues write.

Korean Population May Differ

The 13.5% of the patients who moved from the intermediate- to the low-risk group after researchers implemented the ATA 2015 RSS instead of the ATA 2009 RSS was smaller than that in a previous report, which showed 30% migration.

The reason may have to do with the fact that extrathyroidal extension and lateral lymph-node metastases rates are higher in Korea than they are in Western countries, and aggressive features such as multifocality, bilaterality, and central lymph node metastases are also more common, Dr Lee and colleagues note.

Alternatively, they say, aggressive papillary thyroid cancer might have been higher because the study patients were mostly managed at a tertiary referral hospital.

The authors have no relevant financial relationships.

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Thyroid. 2017;27:174-181. Abstract

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