A proposed clinical scoring system for initiation of lenvatinib treatment in radioiodine-refractory thyroid cancer patients.

[PURPOSE] The optimal timing for starting lenvatinib treatment in patients with radioiodine-refractory differentiated thyroid cancer (RR-DTC) has long been controversial because of the relatively slow-growing nature of differentiated thyroid cancer. The aim of this study was to establish a scoring system using known clinical factors to simplify decision-making in when to start lenvatinib in RR-DTC patients.

[METHODS] We retrospectively analyzed RR-DTC patients treated with lenvatinib. We developed the clinical indication scoring algorithm on the basis of age, tumor-related symptoms, histology, metastatic sites, neutrophil-to-lymphocyte ratio, size of lung metastases, baseline sum of tumor diameters, and tumor-volume doubling time that was used to categorize patients into low-, intermediate-, and high-risk groups.

[RESULTS] A total of 59 patients were analyzed; 13 low-risk, 36 intermediate-risk, and 10 high-risk. The respective median progression-free survival from the initiation of lenvatinib was 93.7 months in the low-risk group, 20.3 months in the intermediate-risk group, and 6.2 months in the high-risk group (p < 0.02). Patients in the high-risk group had significantly worse overall survival compared with those in the low-risk (hazard ratio [HR] 6.59, 95% confidence interval [CI] 1.25-34.90, p < 0.03) or intermediate-risk (HR 2.99, 95% CI 1.03-8.63, p < 0.05) group. Using our proposed algorithm, patients in the intermediate-risk group showed treatment outcomes similar to that were observed in the pivotal trial of lenvatinib, and were the optimal patients to start lenvatinib.

[CONCLUSION] Our proposed scoring system can separate treatment outcomes and prognosis of RR-DTC patients treated with lenvatinib. This simple algorithm can be helpful for oncologists in deciding whether to start lenvatinib treatment in patients with RR-DTC.