RET C634*

This case series highlights the following key message: awareness of the dermatologic findings in MTC/MEN2 patients is essential since lesions such as cutaneous lichen amyloidosis might represent the skin signature of the endocrine condition even before the actual endocrine manifestations. These data add to the limited published reports with respect to this particular presentation, noting the fact that RET-C634 is the most frequent pathogenic variant in MEN2-associated lichen amyloidosis; females are more often affected; the interscapular region is the preferred site; the age of diagnosis might be within the third decade of life, while we reported one of the youngest patients with the lesion. The same RET pathogenic variant is not associated with the same dermatologic features as shown in the vignette. The same RET mutation does not mean that all family members will present the same skin anomaly.

OSMR p. G513D may play a role in modifying the evolutionary processes of CLA in subjects co-harboring RET mutations (further studies are necessary to sustain this aspect). Awareness in CLA-positive patients is essential, including the decision of RET testing in selected cases.

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

Further structure-based computational studies revealed a significant capability of the most active compounds to the complex RET tyrosine kinase domain. The interesting antiproliferative results supported by in silico predictions suggest that these compounds may represent a starting point for the development of a new series of small heterocyclic molecules for the treatment of MTC.

D898_E901 RET deletion is a gain-of-function mutation and responds to tyrosine kinase inhibitors in MTC. RET Δ898-901 mutant is sensitive to selpercatinib and vandetanib, and acquired resistance to selpercatinib may develop via RET-independent mechanisms.

On the basis of adequate perioperative preparation, surgical resection is the most effective and preferred treatment for this type of disease. Laparoscopic surgery is minimally invasive, safe, and effective by stages. Mutations in the RET proto-oncogene may lead to medullary spongy kidneys in multiple endocrine neoplasia 2.

The V804M RET variant has been often associated with MTC or MEN2A phenotypes [1]. However, the variable expression of this variant may lead to a mild clinical phenotype or even absence of MTC/MEN2A manifestations. Hence, active surveillance as opposed to radical surgery like prophylactic thyroidectomy would be more beneficial in patients with no clinical or biochemical evidence of disease.

1)This is the largest study comprising 61 patients after screening 24 family members in India. 2)Synchronous presentation of MEN2 with PCC and MTC is 67% vs 17% in western literature in Index patients.3)MEN2 syndrome should be suspected in patients with MTC and young-onset PCC and all first-degree relatives of index patients with this syndrome*Unless otherwise noted, all abstracts presented at ENDO must not be released to the press or the public until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins.

The ClinVar accession number for the present variants are SCV002028348, and SCV002028352 to SCV002028361. Genetic variants in VHL, SDHB and RET were identified in Chinese PPGL patients, which contributed to the knowledge of the genetic etiology and clinical outcome of these tumors.

Additionally, we show that the RET ECD dimer can form complexes with at least two of the canonical RET ligands and that these complexes form very different structures than wild-type RET ECD upon ligand binding. In conclusion, this structural analysis of cysteine-mutant RET ECD suggests a potential key mechanism of cancer induction in MEN2A, both in the absence and presence of its native ligands, and may offer new targets for therapeutic intervention.

Pts received RETi after a median number of 1 treatment line (range 0‐6) and 83% had received vandetanib (V) prior to RETi... By‐pass resistance MA may be the most frequent mechanism of progression under RETi. More aggressive histology may arise following proghression; further explorations are warranted.

MEN2A-CLA may be the early clinical manifestation of MEN2A and most frequently occurred along with RET-C634 variant. To facilitate the recognition of MEN2A-CLA, to combine family investigation and screening of RET variant are helpful for early diagnosis and standardized treatment, which can improve the long-term outcome of MEN2A-specific tumors.

Analysis of prospectively collected MTC cases during a 27-year period revealed that 21.6% of Slovenian patients are RET PV carriers. Sixty-two percent of families had none of the associated endocrinopathies, confirming the thesis that FMTC is the most common presentation. This could suggest using risk-stratified management approaches when screening for PHEO and PHPT in RET PV carriers. However, more studies are needed to evaluate potential genetic risk modifiers as well as safety, improved quality of life, and medical cost reduction in the case of a patient-oriented approach.

Selective RET inhibitors selpercatinib and pralsetinib were recently approved by the FDA and EMA for patients with RET-dependent NSCLC and thyroid cancers. APS03118 is a novel highly selective next-generation RET inhibitor that possesses potent in vitro and in vivo activity against a diverse range of RET alterations, including SFMs-mediated resistance. A first-in-human phase 1 trial for patients with RET-driven solid tumors with activating RET alterations is planned for 2022.

For the treatment of advanced/metastatic MTC, no specific preference of sequencing systemic agents was observed in the first- and second-line settings. Considering the recent approval of selective RET inhibitors for patients with RET-mutant MTC, future research should investigate how treatment patterns evolve for these patients.

We suggest that the tumorigenic potential conferred by the D631Y mutation is lower than that conferred by the C634R/W mutation, but higher than that conferred by C630Y. Thus, the risk level of the RET D631Y variant appears to be higher than that of C630Y and lower than that of C634R/W.

RET mutation detection is a promising/golden screening test and provides an accurate presymptomatic diagnostic test for at-risk carriers (the siblings and offspring of the patients) to consider prophylactic thyroidectomy. Thus, according to the ATA recommendations, the screening of the RET proto-oncogene is indicated for patients with MTC.

Cabozantinib (30.0%), vandetanib (30.0%), sorafenib (17.2%), and lenvatinib (4.9%) were the most common first-line treatments. Among 49 patients who received second-line treatment, most received cabozantinib (22.4%), vandetanib (20.4%), lenvatinib (12.2%), or sunitinib (12.2%)... More than one-third of patients with advanced/metastatic MTC were not tested for RET mutation as recommended by national guidelines throughout the study period. For the treatment of advanced/metastatic MTC, no specific preference of sequencing systemic agents was observed in the first- and second-line settings. The estimated OS is consistent with that observed from Surveillance, Epidemiology, and End Results database for patients with de novo metastatic MTC.

Moreover, simultaneous surgery for coexistent PHEO and either MTC or HPTH is an approach of choice to use as an alternative treatment pattern. Recognition of MEN2A-related CLA and subsequently early screening of RET mutation may be favorable for timely management of MEN2A-specific tumors.

These data are largely consistent with current evidence-based recommendations in the clinical practice guidelines. Diversity of RET variants or carriers may involve a different natural disease course. Further large-scale targeted sequencing studies will serve as an accurate and cost-effective approach to investigating MEN2 genotype-phenotype correlations for discovery of rare or unknown variants of RET.