New Treatment for Radioactive Iodine–Refractory Differentiated Thyroid Cancer

Radioactive iodine–refractory differentiated thyroid cancer (RAIR-DTC) is a rare and aggressive form of thyroid cancer that does not respond to radioactive iodine treatment, which is the standard treatment for most types of thyroid cancer. RAIR-DTC is typically diagnosed when cancer cells continue to grow or spread despite receiving radioactive iodine therapy, which can result in a poor prognosis and limited treatment options for patients. There is a significant unmet need for effective treatments for RAIR-DTC, and clinical trials are ongoing to evaluate new therapies that may provide hope for patients with this challenging disease.

Apatinib, a highly selective vascular endothelial growth factor (VEGFR-2) inhibitor, is being studied as a possible treatment option for these patients.

A phase 3 randomized clinical trial was conducted on 92 patients with progressive locally advanced or metastatic RAIR-DTC to evaluate the efficacy and safety of apatinib. The trial was conducted in 21 sites between February 17, 2017, and March 2, 2020.

Clinical trial

The patients were randomly assigned (1:1) to receive apatinib, 500 mg/d, or a placebo. Patients who developed progression while receiving placebo were allowed to cross over to apatinib.

The primary endpoint of the study was investigator-assessed progression-free survival (PFS). Secondary endpoints included overall survival, objective response rate (ORR), disease control rate (DCR), duration of response, time to objective response, and safety.

Results

The results of the study showed that apatinib significantly improved progression-free survival and overall survival compared with placebo. The median PFS was 22.2 months for apatinib compared to 4.5 months for placebo, and the median overall survival was not reached for apatinib compared to 29.9 months for placebo.

The confirmed ORR was 54.3% in the apatinib group compared to 2.2% in the placebo group, and the DCR was 95.7% in the apatinib group compared to 58.7% in the placebo group.

The most common grade 3 or higher-level adverse event in the apatinib group was hypertension. Other treatment-related adverse events included hand-foot syndrome, proteinuria, and diarrhea, none of which occurred in the placebo group.

The findings of this study suggest that apatinib could provide a new treatment option for patients with radioactive iodine–refractory differentiated thyroid cancer. However, further studies are needed to confirm the efficacy and safety of apatinib for this indication.

Conclusion

Apatinib has shown significant clinical benefits in both prolonged PFS and overall survival with a manageable safety profile in patients with progressive locally advanced or metastatic RAIR-DTC. Patients who are not responding to radioactive iodine should discuss this treatment option with their doctor.