RET gene testing should be broadened among patients with medullary thyroid carcinoma (MTC) at diagnosis, during localized disease status, and before the initiation of treatment. This was the conclusion of a study presented at the European Society for Medical Oncology (ESMO) Congress 2021, which is taking place online September 16 to 21, 2021.

The testing is needed because MTC treatment is becoming increasingly personalized and the RET status of a patient is a crucial factor in determining the best treatment option for improved outcomes, the study team wrote.

For the study, a group of researchers led by Urpo Kiiskinen, PhD, a senior research scientist in oncology at Eli Lilly and Company, drew real-world data from the Adelphi Thyroid Cancer Disease-Specific Program and conducted a point-in-time survey between July and December 2020. Medical oncologists and endocrinologists in France, Germany, Italy, Spain, and the United Kingdom took part in the survey. The physicians provided the demographics and testing patterns of 275 patients with MTC.

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The results, which were presented as an electronic poster on September 16, 2021, showed that 75% (207 of 275) of the patients were tested for mutations in the RET oncogene. Of these, 38% (70 patients) were positive. Of patients who were genetically tested, 91 were tested for both germline and somatic mutations, 73 were tested for germline mutations only, and 43 were tested for somatic mutations only. 

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Of those who were genetically tested, 140 patients were tested after a diagnosis of MTC, and 85 were tested before the initiation of treatment. Sixty-nine patients had a known disease state, with 50 having locally advanced or metastatic disease when they were tested.

The tested patients received 0.9 and 1 tests on average in the year before data abstraction for germline and somatic RET mutations, respectively. The most common methods used for testing were polymerase chain reaction and next-generation sequencing, but their use varied across different countries. The types of samples most frequently used for testing were tissue and blood samples. 

The greatest barrier to genetic testing also differed by country. It was the cost of testing in Germany, guideline restrictions in the United Kingdom, and delay in obtaining results across Europe.

“Most physicians request a RET gene test for their [patients] with MTC,” the researchers concluded. The study abstract is published on the ESMO website. 


Williams R, Hess LM, Puri T, et al. Real-world study of rearranged during transfection [RET] testing in patients [pts] with medullary thyroid cancer [MTC] in Europe [EU5]. Abstract presented at: European Society for Medical Oncology (ESMO) Congress 2021; September 16-21, 2021; Virtual.