Clinical Trial Evaluates Monotherapy vs Combination Therapy for Thyroid Cancer

According to the most recent data, 900,000 patients are living with a diagnosis of thyroid cancer in the United States alone. It is estimated that 44,000 new cases of thyroid cancer are diagnosed each year with approximately 2,000 deaths annually.

Thyroid cancer is a type of cancer that affects the thyroid gland, a butterfly-shaped gland located in the neck that produces hormones that regulate the body's metabolism. In some cases, thyroid cancer can be treated with radioactive iodine therapy. However, in some cases, the cancer may become resistant to this treatment, known as radioactive iodine refractory thyroid cancer.

Dabrafenib is a type of drug called a BRAF inhibitor, which means it blocks the activity of a protein called BRAF, which is mutated in many cases of thyroid cancer. Trametinib is a type of drug called a MEK inhibitor, which means it blocks the activity of a protein called MEK, which is downstream of BRAF in the same pathway. By blocking these proteins, these drugs can slow down the growth of cancer cells.

While dabrafenib has already shown its beneficial effects in refractory thyroid cancer, the efficacy of its combination with trametinib was yet to be determined.

Clinical Trial

A clinical trial was conducted to compare the safety and effectiveness of two treatments for radioactive iodine refractory thyroid cancer: dabrafenib alone and dabrafenib in combination with trametinib.

The trial was a multicenter trial in which 53 patients were randomly assigned to receive one of the two treatments. The efficacy of both treatment regimens was determined by using modified Response Evaluation Criteria in Solid Tumors (RECIST) at 24 weeks of therapy.

The clinical trial found that the combination of dabrafenib and trametinib was not superior to dabrafenib alone in treating radioactive iodine refractory differentiated thyroid cancer with a BRAF mutation. The objective response rate (modified RECIST) was 42% with dabrafenib versus 48% with dabrafenib + trametinib. However, this difference was not statistically significant.

Additionally, the most common treatment-related adverse events included skin and subcutaneous tissue disorders (17/26, 65%), fever (13/26, 50%), hyperglycemia (12/26, 46%) with dabrafenib alone, and fever (16/27, 59%), nausea, chills, fatigue (14/27, 52% each) with dabrafenib + trametinib. No treatment-related deaths were reported in either group.

Conclusion

Overall, the results of this clinical trial have important implications for patients with radioactive iodine refractory differentiated thyroid cancer with a BRAF mutation. It goes on to show that the combination therapy of dabrafenib + trametinib was not superior in efficacy compared to dabrafenib monotherapy in patients with BRAF-mutated radioiodine refractory progressive thyroid cancer.
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