Dynamic risk allows us to adequately select patients with differentiated thyroid cancer who do not require radioiodine treatment

ABSTRACT Objective: The treatment of patients with differentiated thyroid cancer (DTC) was modified in the last decade towards a more individualized approach according to the risk of recurrence (RR). We compared the outcomes of patients with low and intermediate RR (LRR and IRR) who received or did not receive radioiodine remnant ablation (RRA) after assessing the dynamic risk. Materials and methods: We included 307 DTC patients with LRR and IRR submitted to total thyroidectomy. All patients were reclassified according to the dynamic risk stratification (low or high). Patients with high dynamic risk received RRA (141 patients). Results: LRR patients who received RRA presented a frequency of structural incomplete response (SIR) of 5% at the end of the follow-up, compared to 2% in those who did not receive it (p=0.353). IRR patients treated with RRA had a frequency of SIR of 22%, compared to 5% in patients without RRA (p=0.008). Conclusions: This study demonstrates the usefulness of dynamic risk assessment to decide RRA in a cohort with a long-term follow-up. The lower prevalence of SIR at the end of the follow-up in patients who did not receive RRA highlights the adequate selection of those who would not benefit from RRA, even with an intermediate risk of recurrence.

Riesgo dinámico en cáncer diferenciado de tiroides: comparación entre pacientes ablacionados con aquellos no ablacionados de bajo riesgo y riesgo intermedio de recurrencia

RESUMEN El enfoque actual de los pacientes con carcinoma diferenciado de tiroides (CDT) es individualizado de acuerdo al riesgo de recurrencia (RR) de la enfermedad. La clasificación estática del RR inicial podría mejorarse al aplicar el denominado riesgo dinámico, que resulta de adicionar al RR, los hallazgos que surgen durante el seguimiento. Los objetivos de este trabajo fueron comparar pacientes ablacionados de bajo RR y riesgo intermedio estático que recibieron ablación inmediatamente luego de la cirugía vs. los no ablacionados de bajo riesgo dinámico. Secundariamente, comparar la población de pacientes ablacionados de bajo riesgo estático vs. los no ablacionados de bajo riesgo dinámico. Se incluyeron 412 pacientes, 309 ablacionados (Grupo 1: G1), y 103 no ablacionados (Grupo 2: G2). El G1 también incluyó a 29 pacientes que fueron ablacionados al observar el riesgo dinámico (Tg bajo terapia hormonal > 5 ng/ml). La frecuencia de respuesta estructural incompleta (REI) al inicio y al final del seguimiento fue mayor en el grupo de pacientes ablacionados de bajo RR y riesgo intermedio estático comparados con los no ablacionados de bajo riesgo dinámico (11,3% vs 0,9%: p=<0,001). La frecuencia de respuesta excelente al final del seguimiento fue mayor en los no ablacionados de bajo riesgo dinámico vs. ablacionados de bajo RR y riesgo intermedio estático (72,8% vs 62,1%: p=0,058). En conclusión, los pacientes ablacionados de bajo RR y riesgo intermedio presentaron una mayor frecuencia de REI que los no ablacionados adecuadamente seleccionados, al tener en cuenta el RR inicial. En cambio, al comparar pacientes ablacionados de bajo RR estático vs. no ablacionados de bajo riesgo dinámico, la REI fue similar. Estos resultados avalan la conducta de no ablacionar a aquellos pacientes de riesgo intermedio de recurrencia que presentan en el seguimiento un bajo riesgo dinámico.

ABSTRACT The current approach of patients with differentiated thyroid carcinoma (DTC) is individualized according to the risk of recurrence (RR) of the disease. The static classification of the initial RR could be improved by applying the dynamic risk of recurrence to decide remnant ablation. The dynamic risk definition arise from the findings obtained during the initial follow-up. The aim of this manuscript is to compare the response to treatment in patients with low and intermediate static RR in whom the decision for radioiodine remnant ablation (RRA) was performed immediately after surgery with those non-ablated patients with low dynamic RR. Secondary, to compare the responses to treatment in ablated patients with low static RR compared with those non-ablated low dynamic RR. We included 412 patients, they were divided in two groups Group 1 (G1): n=309 ablated patients and Group 2 (G2): n=103 non-ablated patients. G1 also included 29 patients who received remnant ablation considering the dynamic risk (Tg levels > 5 ng/ml). The initial structural incomplete response (SIR) was greater in G1 compared with G2 (11.3% vs 0.9%: p = <0.001). The frequency of an excellent response at the end of follow-up was similar in G2 compared with low initial RR of G1 (72.8% vs. 62.1%: p = 0.058). In conclusion, low and intermediate static RR ablated patients had a higher frequency of SIR compared with non-ablated patients in the dynamic risk assessment. In contrast, the frequency of SIR was similar when ablated patients of low static RR were compared with those non-ablated patients of low dynamic risk. These results show how the dynamic RR helps to move those intermediate RR patients on the low RR decreasing the need for RRA.