RET M918T

These novel findings identify a link between the RET signaling pathway and abnormal osteoblastic bone formation and suggest OPG as a potential biomarker of MTC bone metastases. Patient-derived MTC cells promote osteoblastic lesions in a mouse model.Activating the RET mutation promotes osteoprotegerin.Blocking RET kinase activity inhibits tumor growth and the osteoblastic lesion phenotype.High levels of circulating osteoprotegerin are associated with poor overall survival.

Given the rapidly progressive disease, vandetanib was initiated while awaiting molecular testing for rearranged during transfection (RET)-alteration. Following the detection of the RET M918T mutation, treatment was switched to selpercatinib, and rapid tumor response and endocrine symptom resolution were observed. This case highlights the importance of evaluating serum calcitonin, specifically in patients with neuroendocrine carcinoma of unknown primary, where MTC should be considered as a critical differential diagnosis. Thyroid ultrasound should be performed to identify even small lesions of medullary thyroid carcinoma (micro-MTC). Identification of MTC not only leads to targeted therapies that may improve prognosis, but also allows for genetic risk assessment and early intervention in family members when multiple endocrine neoplasia type 2 (MEN2) is suspected.

The current systemic treatment profile for progressive metastatic MTC involves antiangiogenics multikinase inhibitors (MKI), specifically cabozantinib and vandetanib, and high-specific RET inhibitor therapy. Decisions on the timing of systemic therapy initiation in this population should involve multidisciplinary care and individualization on a case-by-case scenario; a comprehensive evaluation of performance status, tumor burden, progression rate, medical comorbidities, possible medication interactions, and goals of care must be considered in a patient-centered approach. This review summarizes the evidence on the safety, efficacy, and limitations of systemic therapies for MTC; the aim is to empower clinicians with the knowledge to optimally manage patients with advanced, progressive, or metastatic MTC.

Our results provided the first comprehensive analysis of RET mutations in Vietnamese MTC patients. The most frequent mutation was p.M918T, followed by p.C634R and p.C618R. Mutations in these three exons were linked to specific histopathological features. Information on mutational profiles of patients with MTC will further aid in the development of targeted therapeutics to ensure effective disease management.

However, it finds the best utility in patients with a lower risk of recurrence and mortality, identifying those rare cases with more aggressive clinical behavior. Conversely, when laterocervical lymph nodes (N1), distant metastasis (M1), or RET mutations, particularly M918T or indels, are already present at diagnosis, the role of IMTCGS in predicting DSS, DMFS, and LRFS becomes less relevant.

From these data, it is clear to see the importance of genetic counseling and RET screening in all first-degree relatives of patients with proven MEN2. The goal should be to subject patients to surgery for prophylactic and not curative purposes, i.e., before the onset of MTC, given the high risk of persistent or recurrent disease also in pediatric/adolescent patients.

RET p.M918T-driven progression of MTC is similar in hereditary and sporadic disease, barring earlier development and more frequent multifocal growth of hereditary MTC. This makes a compelling case for referral of patients with RET p.M918T-driven MTCs to specialist surgical centers.

When comparing RET M918T to RET indels there was no significant difference in time to DMD, DSS, or OS between the groups. Somatic RET mutations do not portend compromised DSS or OS in a cohort of sMTC patients who underwent clinically motivated NGS.

We report a rare case of selpercatinib use for MMFCC. Since RET mutations may occur frequently in MMFCC, selpercatinib could be effective in treating MMFCC.

We previously showed that the multi-kinase inhibitors vandetanib and cabozantinib increase the mitochondrial membrane potential (Δψm) in RET-mutated thyroid tumor cells and that this effect can be exploited to increase mitochondrial enrichment of Δψm-sensitive agents in the tumor cells...The quality of life of one patient significantly improved over a year until the tumor relapsed. This combination of selpercatinib with MitoQ may have therapeutic potential for patients with RET-mutated tumors and intolerant to regular selpercatinib doses.

Bypass resistance may be the most frequent mechanism of progression under RETi. A more aggressive histology may arise following RETi and warrants further investigation.

IMTCGS grading was associated with DSS independently of other clinical, pathological, and molecular factors. Moreover, MTC grading was associated with RET and RAS patterns, which explains, at least in part, the molecular basis of the aggressive behavior of high-grade MTC.