The use of selpercatinib (Retevmo®) resulted in partial responses (PR) for patients with advanced thyroid cancers, including medullary thyroid carcinoma (MTC), with few adverse events, according to a case series published in Current Oncology.
During the series, 2 patients with advanced MTC achieved PR after treatment with selpercatinib. Both patients received selpercatinib as second-line therapy following total thyroidectomy (TT) and treatment with vandetanib (Caprelsa®) once disease recurrence was detected.
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The first patient was a 62-year-old male who had received TT 6 years prior and also had lymph node dissection of metastatic MTC. Genetic testing confirmed RET germline mutations, and lung metastasis was detected, prompting treatment with vandetanib. His dose of vandetanib was reduced after observing a grade 3 QT corrected (QTc) interval prolongation on ECG. PR was achieved at 12 months, but multiple bone metastases were detected at 30 months of treatment, so vandetanib was discontinued.
No second-line treatments were available at that time in South Korea, so palliative radiation therapy was administered for multiple spine lesions. Eventually, selpercatinib was available for use, but the patient had received a percutaneous endoscopic gastrostomy (PEG) due to difficulties swallowing.
Selpercatinib was administered through the PEG after being dissolved in warm water. The patient experienced hypercalcemia and reduced the estimated glomerular filtration rate at 12 weeks of therapy, and it was paused. After the patient recovered, selpercatinib therapy was resumed, and no more issues were reported. The patient has had a partial response for 11 months after 1 year of treatment.
The second patient was a 67-year-old female who received TT followed by vandetanib treatment. Vandetanib was discontinued 24 months later after the patient experienced a grade 3 QTc prolongation and grade 2 vision blurring.
Metastatic MTC was detected in multiple lymph nodes, the liver, bone, and the choroid of the eye and confirmed to have germline RET mutations. She received selpercatinib through transarterial embolization, and at 1 month of treatment, PR of the choroidal lesion was observed. PR was observed in lesions of the chest and abdomen, while the stable disease was observed in neck lesions.
“Despite facing varying clinical obstacles of the real world, selpercatinib safely proved remarkable therapeutic efficacy, although drug safety and durability through long-term use should be further validated,” the authors said.
The case series also highlighted 2 patients with advanced papillary thyroid carcinoma who were treated with selpercatinib. Both achieved a PR and had alleviation of symptoms related to the lesions.
Reference
Baek HS, Ha J, Ha S, et al. Initial experiences of selective RET inhibitor selpercatinib in adults with metastatic differentiated thyroid carcinoma and medullary thyroid carcinoma: Real-world case series in Korea. Curr Oncol. Published online March 3, 2023. doi:10.3390/curroncol30030229
