Thyroid Cancer: Role of RET and Beyond

Efficacy and safety of selpercatinib in treating RET-altered MTC: A single-arm meta-analysis

Background

Selpercatinib is effective in the treatment of RET-altered medullary thyroid carcinoma (MTC). This study aimed to evaluate the efficacy and safety of selpercatinib in the treatment of patients with RET-altered MTC.

Methods

PubMed, Embase, the Cochrane Library, and ClinicalTrials.gov were searched from their inception to April 5, 2024. Outcomes included complete response (CR), partial response (PR), stable disease (SD), objective response rate (ORR), disease control rate (DCR), and adverse events (AEs). We carried out a meta-analysis of these studies and exploratory subgroup analyses. The effect sizes for all pooled results were presented as 95% confidence intervals with upper and lower limits.

Results

The pooled CR, PR, and SD rates for all patients were 10%, 59%, and 26%, respectively. The pooled ORR in all patients was 70%, while the pooled ORR in pre-treated and non-pre-treated groups were 67% and 70%, respectively. The pooled DCR in all patients was 95%, while the pooled DCR in pre-treated and non-pre-treated groups were 96% and 95%, respectively. The most common AEs associated with selpercatinib were hypertension, alanine aminotransferase (ALT) increased and aspartate aminotransferase (AST) increased.

Conclusion

Selpercatinib offers significant benefits to patients with RET-altered MTC with assessable CR, PR, SD, ORR, and grade 3-4 AEs; however, treatment-related AEs should be considered.

Durable response to low-dose pralsetinib in a renal insufficient patient with NSCLC harboring concurrent CCDC6-RET, LINCO1264-RET, and SEMA5A-RET fusions: A case report

INTRODUCTION

RET-rearranged fusions have been considered as oncogenic drivers in 1% to 2% of non-small cell lung cancers (NSCLC). ARROW study has demonstrated a new selective RET tyrosine kinase inhibitors (TKIs) shows remarkable and durable responses in RET-rearranged NCSLC. In this study mainly recruited patients with common fusion partners KIF5B and CCDC6. There is still a lack of definitive conclusions about effective of rare RET fusion variants to anti-RET therapies.

CASE REPORT

A Chinese 58-year-old female renal insufficient patient with no history of smoking was diagnosed as stage IIIA (T2N2M0) lung adenocarcinoma. Next-generation sequencing targeting 520 cancer-related genes was performed on the pleural effusion samples and revealed 2 novel RET fusions LINCO1264-RET and SEMA5A-RET, concomitant with a common CCDC6-RET.

MANAGEMENT AND OUTCOME

The patient was first treated with multiple lines of chemotherapy and switched to lenvatinib but failed to respond. Due to renal insufficiency, she subsequently received pralsetinib with gradually reduced dosages (400 mg-300 mg-200 mg-100 mg qd) and achieved a partial response (PR) lasting for more than 10 months, accompanied by the declined allele frequencies of all 3 RET fusions.

DISCUSSION/CONCLUSIONS

We reported the first case of the pralsetinib efficacy in NSCLC with 3 concurrent RET fusions. Our case also indicates the sensitivity of the newly identified RET fusions to this RET selective inhibitor pralsetinib, and highlights the low-dose treatment option for patients with renal insufficient background.

Identification and Validation of Noncanonical RET Fusions in Non-Small-Cell Lung Cancer through DNA and RNA Sequencing

RET fusion has emerged as a targetable driver in non-small-cell lung cancer. A comparative analysis on RET fusions at DNA [DNA sequencing (DNA-seq)] and RNA [RNA sequencing (RNA-seq)] levels was performed in this study. Archived tumor samples from 54 non-small-cell lung cancer patients with DNA-level noncanonical RET fusions were selected for RNA-seq. RNA-seq identified RET fusion transcripts in 41 of 44 samples passing quality control. In the subset of cases harboring RET 3'-end fusions and predicted to produce in-frame proteins (group A; n = 33), RNA-seq identified the same 3'-end fusions in 32 (96.9%). A total of 26 of 32 also had a reciprocal RET 5'-end fusion detected by DNA-seq that was not transcribed. In the subset with DNA-level out-of-frame RET fusions (group B; n = 9), RNA-seq identified in-frame RET fusion transcripts in 8 cases (88.9%). In the subset only identified with a RET 5'-end fusion by DNA-seq (group C; n = 2), RNA-seq detected the corresponding 3'-end fusion in one case. The discordant DNA- and RNA-level fusions observed in group B may be mediated by complex genomic rearrangement events and transcriptional or post-transcriptional processes. In conclusion, DNA-seq demonstrates a high concordance of 96.9% on detecting in-frame RET fusion, but shows a low concordance on detecting out-of-frame RET fusion and RET 5'-end fusion compared with RNA-seq.

Discovery of N-Trisubstituted Pyrimidine Derivatives as Type I RET and RET Gatekeeper Mutant Inhibitors with a Novel Kinase Binding Pose

Mutations of the rearranged during transfection (RET) kinase are frequently reported in cancer, which make it as an attractive therapeutic target. Herein, we discovered a series of N-trisubstituted pyrimidine derivatives as potent inhibitors for both wild-type (wt) RET and RETV804M, which is a resistant mutant for several FDA-approved inhibitors. The X-ray structure of a representative inhibitor with RET revealed that the compound binds in a unique pose that bifurcates beneath the P-loop and confirmed the compound as a type I inhibitor. Through the structure-activity relationship (SAR) study, compound 20 was identified as a lead compound, showing potent inhibition of both RET and RETV804M. Additionally, compound 20 displayed potent antiproliferative activity of CCDC6-RET-driven LC-2/ad cells. Analysis of RET phosphorylation indicated that biological activity was mediated by RET inhibition. Collectively, N-trisubstituted pyrimidine derivatives could serve as scaffolds for the discovery and development of potent inhibitors of type I RET and its gatekeeper mutant for the treatment of RET-driven cancers.

Efficacy and safety of selpercatinib in Chinese patients with advanced RET-altered thyroid cancers: results from the phase II LIBRETTO-321 study

Background:

Selpercatinib, a highly selective and potent REarranged during Transfection (RET) kinase inhibitor, is effective in advanced RET-altered thyroid cancer (TC). However, the efficacy and safety in Chinese patients are unknown.

Patients and methods:

In the open-label, multi-center phase II LIBRETTO-321 (NCT04280081) study, Chinese patients with advanced solid tumors harboring RET alterations received selpercatinib 160 mg twice daily. The primary endpoint was objective response rate (ORR; RECIST v1.1) by independent review committee (IRC). Secondary endpoints included duration of response (DoR) and safety. Efficacy was assessed in the primary analysis set [PAS; treated patients with RET fusion-positive TC or RET-mutant medullary TC (MTC) confirmed by central laboratory] and all enrolled patients with MTC.

Results:

Of 77 enrolled patients, 29 had RET-mutant MTC and one had RET fusion-positive TC. In the PAS (n = 26), the ORR by IRC was 57.7% [95% confidence interval (CI), 36.9–76.6]. Median DoR was not reached and 93.3% of responses were ongoing at a median follow-up of 8.7 months. In all enrolled MTC patients (n = 29), the ORR by IRC was 58.6% (95% CI, 38.9–76.5). One RET fusion-positive TC patient treated for 23.4 weeks achieved a partial response at week 8 that was ongoing at cutoff. In the safety population (n = 77), 59.7% experienced grade ⩾3 treatment-emergent adverse events (TEAEs). TEAEs led to dose reductions in 32.5% (n = 25) and discontinuations in 5.2% [n = 4; 3.9% (n = 3) considered treatment related] of patients.

Conclusions:

Selpercatinib showed robust antitumor activity and was well tolerated in Chinese patients with advanced RET-altered TC, consistent with global data from LIBRETTO-001 (NCT04280081).

ClinicalTrials.gov Identifier:

NCT04280081 (first posted Feb 21, 2020)

RET Fluorescence In Situ Hybridization Analysis Is a Sensitive but Highly Unspecific Screening Method for RET Fusions in Lung Cancer

INTRODUCTION

RET gene fusions are established oncogenic drivers in 1% of NSCLC. Accurate detection of advanced patients with RET fusions is essential to ensure optimal therapy choice. We investigated the performance of fluorescence in situ hybridization (FISH) as a diagnostic test for detecting functional RET fusions.

METHODS

Between January 2016 and November 2019, a total of 4873 patients with NSCLC were routinely screened for RET fusions using either FISH (n = 2858) or targeted RNA next-generation sequencing (NGS) (n = 2015). If sufficient material was available, positive cases were analyzed by both methods (n = 39) and multiple FISH assays (n = 17). In an independent cohort of 520 patients with NSCLC, whole-genome sequencing data were investigated for disruptive structural variations and functional fusions in the RET and compared with ALK and ROS1 loci.

RESULTS

FISH analysis revealed RET rearrangement in 48 of 2858 cases; of 30 rearranged cases double tested with NGS, only nine had a functional RET fusion. RNA NGS yielded RET fusions in 14 of 2015 cases; all nine cases double tested by FISH had RET locus rearrangement. Of these 18 verified RET fusion cases, 16 had a split signal and two a complex rearrangement by FISH. By whole-genome sequencing, the prevalence of functional fusions compared with all disruptive events was lower in the RET (4 of 9, 44%) than the ALK (27 of 34, 79%) and ROS1 (9 of 12, 75%) loci.

CONCLUSIONS

FISH is a sensitive but unspecific technique for RET screening, always requiring a confirmation using an orthogonal technique, owing to frequently occurring RET rearrangements not resulting in functional fusions in NSCLC.

Kinome scale profiling of venom effects on cancer cells reveals potential new venom activities

The search for novel and relevant cancer therapeutics is continuous and ongoing. Cancer adaptations, resulting in therapeutic treatment failures, fuel this continuous necessity for new drugs to novel targets. Recently, researchers have started to investigate the effect of venoms and venom components on different types of cancer, investigating their mechanisms of action. Receptor tyrosine kinases (RTKs) comprise a family of highly conserved and functionally important druggable targets for cancer therapy. This research exploits the novelty of complex venom mixtures to affect phosphorylation of the epidermal growth factor receptor (EGFR) and related RTK family members, dually identifying new activities and unexplored avenues for future cancer and venom research. Six whole venoms from diverse species taxa, were evaluated for their ability to illicit changes in the phosphorylated expression of a panel of 49 commonly expressed RTKs. The triple negative breast cancer cell line MDA-MB-468 was treated with optimised venom doses, pre-determined by SDS PAGE and Western blot analysis. The phosphorylated expression levels of 49 RTKs in response to the venoms were assessed with the use of Human Phospho-RTK Arrays and analysed using ImageLab 5.2.1 analysis software (BioRad). Inhibition of EGFR phosphorylation occurred with treatment of venom from Acanthoscurria geniculata (Theraphosidae), Heterometrus swammerdami (Scorpionidae), Crotalus durissus vegrandis (Crotalidae) and Naja naja (Elapidae). Western green mamba Dendroaspis viridis venom increased EGFR phosphorylation. Eph, HGFR and HER were the most affected receptor families by venoms. Whilst the importance of these changes in terms of effect on MDA-MB-468 cells' long-term viability and functionality are still unclear, the findings present exciting opportunities for further investigation as potential drug targets in cancer and as tools to understand better how these pathways interact.

Comparison of pediatric and adult medullary thyroid carcinoma based on SEER program

To compare the clinicopathological characteristics and survival outcomes of children and adult diagnosed with medullary thyroid carcinoma (MTC). MTC patients were extracted from the Surveillance, Epidemiology and End Results (SEER) database from 1998 to 2016, followed by stratification into pediatric (< 20 years) or adult (≥ 20 years) groups. In total, 2,197 patients (110 pediatric and 2087 adult) with MTC were identified. Pediatric patients were more likely to have localized stage (70.0% vs. 51.6%), negative regional nodes (48.2% vs. 30.8%) and receive total/subtotal thyroidectomy surgery (97.3% vs. 85.3%). Moreover, CSS and OS rates were significantly higher in pediatric patients (both P < 0.001). Multivariable Cox regression analysis revealed that adult patients were significantly correlated with worse CSS and OS rates [(CSS: HR 11.60, 95% CI 1.62–83.02, P = 0.015); (OS: HR 5.63, 95% CI 2.08–15.25, P = 0.001)]. Further stratified analysis indicated that pediatric group might have significant better CSS and OS for patients with more advanced stage. Patients in the pediatric group were more likely to have earlier stage. Moreover, the prognosis of pediatric MTC patients was significantly better than that in adult patients.

Genomic characterization of high-recurrence risk papillary thyroid carcinoma in a southern Chinese population

BACKGROUND

The objective of this study was to investigate genetic variations and the relationships between these genetic variations and clinicopathological features of high-recurrence risk papillary thyroid carcinoma in a southern Chinese population.

METHODS

One hundred sixty-eight patients of high-recurrence risk papillary thyroid carcinoma were recruited for this study from 2017 to 2018. Formalin-fixed paraffin-embedded tissue and the data of clinicopathological characteristics were all collected and analyzed from these patients. We used next-generation sequencing technology to investigate the targeted gene mutations and gene fusions of the pathology specimens.

RESULTS

The frequency of candidate tumor driver gene mutation was 85.1% in 143 patients, including BRAF V600E mutation in 119 patients(70.8%), RET fusion in 13 patients(7.7%), TERT promoter mutations in 11 patients(6.5%), RAS (HRAS, NRAS, KRAS) gene mutations in 10 patients(6.0%), and other mutations involving TP53, PIK3CA, AKT1, PTEN and NTRK1. Concomitant presence of more than two genetic aberrations was seen in 27 patients (16.1%). Our study showed that BRAF V600E mutation is highly correlated with conventional PTC (p < 0.001), BRAF V600E and TERT promoter mutation duet was associated with older patient age (> 45, p = 0.003) and higher disease stage of III or IV (p = 0.002). RAS gene and BRAF V600E co-mutations were only seen in multifocal PTC (p = 0.015).

CONCLUSION

In our high-recurrence risk PTC cohort, most patients had more than one driver gene aberration. Coexistence of BRAF V600E with TERT promoter mutations or with RAS mutations were significantly correlated with worse clinicopathological characteristics.

Management of treatment-related toxicities in advanced medullary thyroid cancer

PURPOSE OF REVIEW

Tyrosine kinase inhibitors (TKI), predominantly vandetanib and cabozantinib, are increasingly used for management of advanced medullary thyroid cancer. This review aims to discuss the major and serious adverse events associated with TKI.

RECENT FINDINGS

The choice of TKI depends on the patient's existing comorbidities. Patients who have long QT interval should avoid vandetanib and those at risk of gastrointestinal perforation should avoid cabozantinib. Hypertension is common during the first 3 months. Treatments include ACE inhibitors, calcium channel blockers (avoiding verapamil and diltiazem, which are CYP3A4 inhibitors), and beta blockers. Diuretics should be second line because of derangement of electrolytes, which may exacerbate QT interval. As nitric oxide (NO) blockade and ET1 are implicated in the mechanism of hypertension, nitrates and endothelin receptor antagonists may be used. Thromboembolism may require anticoagulation or revascularization procedures. Prolonged QT interval should be treated by dose interruption and reduction, correction of electrolytes, and avoidance of medications, which prolong QTc interval. Diarrhoea is managed symptomatically and with electrolyte replacement, dermatological adverse events with avoidance of exacerbating factors and topical therapies. Thyroid function should be monitored.

SUMMARY

Toxicities are common with TKI use, and management involves symptomatic treatment, avoidance of triggers, dose interruption, and dose reduction.

Canine Thyroid Cancer: Molecular Characterization and Cell Line Growth in Nude Mice

Thyroid cancer is the most common endocrine malignancy in dogs. Dogs and humans are similar in the spontaneous development of thyroid cancer and metastasis to lungs; however, thyroid cancer has a higher incidence of metastasis in dogs. This study developed a preclinical nude mouse model of canine thyroid cancer using a canine thyroid adenocarcinoma cell line (CTAC) and measured the expression of important invasion and metastasis genes in spontaneous canine thyroid carcinomas and CTAC cells. CTAC cells were examined by electron microscopy. Short tandem repeat analysis was performed for both the original neoplasm and CTAC cells. CTAC cells were transduced with luciferase and injected subcutaneously and into the tail vein. Tumors and metastases were monitored using bioluminescent imaging and confirmed with gross necropsy and histopathology. Invasion and metastasis genes were characterized in 8 follicular thyroid carcinomas (FTCs), 4 C-cell thyroid carcinomas, 3 normal thyroids, and CTAC cells. CTAC cells grew well as xenografts in the subcutis, and they resembled the primary neoplasm. Metastasis to the kidney and lung occurred infrequently following subcutaneous and tail vein injection of CTAC cells. STR analysis confirmed that CTAC cells were derived from the original neoplasm and were of canine origin. Finally, 24 genes were differentially expressed in spontaneous canine thyroid carcinomas, CTAC, and normal thyroids. This study demonstrated the usefulness of a nude mouse model of experimental canine thyroid carcinoma and identified potential molecular targets of canine follicular and C-cell thyroid carcinoma.

Prolonged Response to Regorafenib in a Patient with Iodine Refractory Thyroid Cancer

Thyroid cancer is the most common type of endocrine malignancy. Cornerstones of thyroid cancer treatment include surgery, radioactive iodine ablation, and thyroid stimulating hormone suppression. The National Comprehensive Cancer Network guidelines recommend two tyrosine kinase inhibitors for thyroid cancer patients who are non-responsive to iodine: sorafenib and lenvatinib. Another oral kinase inhibitor, regorafenib, is not considered standard of care treatment for differentiated thyroid cancer. The chemical structures of regorafenib and sorafenib differ by a single fluorine atom. Given the significant improvement in progression-free survival (PFS) of sorafenib compared to placebo demonstrated in the phase 3 DECISION trial, we report on a patient with iodine-refractory follicular thyroid cancer treated with regorafenib as part of a phase 1 clinical trial. A 75 year old woman was diagnosed with follicular thyroid carcinoma in 2006 and initiated on treatment with regorafenib in 2011. She has completed 76 cycles with stable disease and pulmonary metastases 34% smaller than baseline.

Medullary Thyroid Cancer: Overview and Case Study of a Rare Cancer

BACKGROUND

Medullary thyroid cancer (MTC) is a rare cancer that has historically been managed by endocrinologists. In 2011, the first of several multi- targeted tyrosine kinase inhibitors was approved as treatment for MTC. These drugs have changed the management of MTC to teams that include oncologists and oncology nurses.

OBJECTIVES

This article illustrates MTC diagnostics, surveillance, management of adverse drug reactions, and disease progression through a case study.

METHODS

An overview of MTC is offered, followed by an in-depth case study that examines MTC from the patient's perspective.

FINDINGS

Oncology nurses can influence patient outcomes through the provision of patient education, support, and management of disease and treatment complications.

Targeting of RET oncogene by naphthalene diimide-mediated gene promoter G-quadruplex stabilization exerts anti-tumor activity in oncogene-addicted human medullary thyroid cancer

Medullary thyroid cancer (MTC) relies on the aberrant activation of RET proto-oncogene. Though targeted approaches (i.e., tyrosine kinase inhibitors) are available, the absence of complete responses and the onset of resistance mechanisms indicate the need for novel therapeutic interventions. Due to their role in regulation of gene expression, G-quadruplexes (G4) represent attractive targets amenable to be recognized or stabilized by small molecules. Here, we report that exposure of MTC cells to a tri-substituted naphthalene diimide (NDI) resulted in a significant antiproliferative activity paralleled by inhibition of RET expression. Biophysical analysis and gene reporter assays showed that impairment of RET expression was consequent to the NDI-mediated stabilization of the G4 forming within the gene promoter. We also showed for the first time that systemic administration of the NDI in mice xenotransplanted with MTC cells resulted in a remarkable inhibition of tumor growth in vivo. Overall, our findings indicate that NDI-dependent RET G4 stabilization represents a suitable approach to control RET transcription and delineate the rationale for the development of G4 stabilizing-based treatments for MTC as well as for other tumors in which RET may have functional and therapeutic implications.