Is ATA Risk Stratification Still a Reliable Predictor of Response in DTC?

Oncologists who specialize in differentiated thyroid cancer (DTC) commonly use the American Thyroid Association (ATA) 2015 guidelines for risk stratification in patients. A real-world study assessed the performance of this system in patients with DTC and discovered that the system is reliable for predicting short-term outcomes.

“The ATA risk stratification system is a reliable predictor of short-term outcomes in patients with DTC in real-world clinical settings characterized by appreciable treatment-center heterogeneity in terms of size, location, level of care, diagnostic resources, and local management strategies,” Durante et al concluded, in the paper.

A report published in Thyroid provided prospective 1-year data from 2000 patients who were treated in the real-world across 50 centers throughout Italy. Patients were found in the Italian Thyroid Cancer Observatory, an online database governed by the Thyroid Cancer Center of the Sapienza University of Rome. To be selected for the study, each patient record was required to have a histological diagnosis of DTC, papillary thyroid cancer (PTC), follicular thyroid cancer (FTC), or poorly DTC and variants of these diseases. All patients were also required to have available information on treatment and pathological characteristics for investigators to determine their risk using the ATA risk stratification system. The third and final requirement was full information about each patients’ 1-year follow-up visit which was needed to estimate response to treatment.

Following the exclusion of 4610 cases from the database of 6867, the final cohort was compiled of 2071 patients from 40 centers. In 1109 patients (53.6%), the ATA risk of persistent and/or recurrent disease was classified as low, 796 patients (38.4%) were classified as intermediate risk, and 166 (8.0%) were classified as high risk.

Investigators led by Cosimo Durante, MD, found that in the overall population, 1576 patients (76.1%) had an excellent response, 376 (17.8%) had an indeterminate response, 33 (1.6%) had a biochemical incomplete responses, and structural incomplete responses were found in 86 patients (4.2%), which showed progressive increase with the baseline risk levels estimated as 1.5% in the low-risk patients, 5.7% in intermediate-risk patients, and 14.5% in high-risk patients. Prior treatment did impact responses to treatment at 1-year evaluation.

Of the patients with prior radioactive iodine remnant ablation, excellent responses were observed in 921 (77.3%), indeterminate responses were seen in 168 (14.1%), biochemical incomplete responses were observed in 33 (2.8%), and structural incomplete responses were observed in 69 patients (5.8%). Among those who had a total thyroidectomy, 655 (81.1%) had excellent responses, 137 (17%) had indeterminant responses, no patients had a biochemical incomplete response, and structural incomplete responses were seen in 15 patients (1.9%). Finally, among patients who had a thyroid lobectomy, 71 patients (97.3%) had an indeterminant response and 2 (2.7%) had a structural incomplete response. No patients in the thyroid lobectomy group had an excellent response or biochemical incomplete response.

A significant predictor of response to treatment was determined to be ATA risk class assigned at baseline, which was observed again at 1-year follow-up. There was no data for the low-risk group; however, the odds ratios (OR) for response to treatment in the intermediate-risk group was 4.67 (95% CI, 2.59-8.43; P <.0001). In the high-risk group, the OR was 16.48 (95% CI, 7.87-34.5; P <.0001). The results also showed a high probability of suboptimal response in patients classified as intermediate- to high-risk. Specifically, the OR that intermediate-risk patients would have a response to treatment was 1.68 (95% CI, 1.34-2.10; P <.0001). The OR that high-risk patients would respond was 3.23 (95% CI, 2.23-4.67; P <.0001).

Another assessment conducted during the study looked at how individual practice reporting impacted the performance of initial disease risk. The assessment included both academic and non-academic cancer centers. No impact was found.

“Our findings demonstrate that the ATA risk stratification system for recurrent/persistent disease is indeed a reliable predictor at the 1-year follow-up evaluation, independent of treatment centers. This is true in spite of the fact that the likelihood of a “less-than-excellent” response varies across treatment centers, probably as a result of between-center differences in surgical volumes, case mixes, the availability of diagnostic tools, and/or other factors,” wrote Durante et al.

_Reference:

_{Durante C, Grani G, Zaelli MC, et al. Real-world performance of the American Thyroid Association risk estimates in predicting 1-year differentiated thyroid cancer outcomes: A prospective multicenter study of 2000 patients. Thyroid. Published online July 1, 2020. doi: 10.1089/thy.2020.0272}