A case of neoadjuvant targeted therapy with pralsetinib for locally advanced lung adenocarcinoma with RET fusion mutation.

This case report details the successful treatment of a 68-year-old male patient with locally advanced RET-rearranged lung adenocarcinoma using neoadjuvant pralsetinib. The patient initially presented with a suspicious right upper lobe nodule, which was later diagnosed as lung adenocarcinoma following genetic testing that revealed a RET exon 12 fusion. After 2 months of neoadjuvant treatment with pralsetinib, a significant radiological response was observed, with a reduction in tumor size and metabolic activity. Subsequently, the patient underwent video-assisted thoracoscopic right upper lobectomy and mediastinal lymph node dissection. Postoperative pathological analysis revealed a major pathological response, with only 5% residual tumor cells in the primary lesion and no viable tumor cells in the lymph nodes. Postoperative pathological staging of TNM was ypT1aN0M0, stage IA1(AJCC, 8th edition). The patient recovered well after surgery, demonstrating the potential efficacy of neoadjuvant pralsetinib in locally advanced RET-rearranged lung adenocarcinoma. However, further clinical validation is required to establish the role of neoadjuvant targeted therapy and postoperative adjuvant therapy in this patient population.

Pralsetinib as neoadjuvant therapy for RET-Altered differentiated thyroid cancer: Two case reports.

BACKGROUND: 5-10% of thyroid cancers are at locally advanced stage. Neoadjuvant targeted therapy will likely create surgical opportunities for these patients with unresectable or borderline resectable tumors. Pralsetinib, a RET inhibitor, has been approved for advanced or metastatic RET-altered thyroid cancer. However, there is no evidence on the efficacy of pralsetinib as neoadjuvant therapy in locally advanced RET-altered thyroid cancer. CASE REPORT: Two patients with locally advanced pappilary thyroid carcinoma (PTC) were treated with pralsetinib (400 mg daily) to reduce tumor size and increase the chance of R0 resection. Both PTCs, characterized by RET-fusion, underwent successful R0 resection without major surgical complications after 4-months neoadjuvant pralsetinib. CONCLUSION: There is a potential for pralsetinib as a neoadjuvant treatment in PTC with RET-fusion.

Efficacy and safety of pralsetinib in patients with RET fusion positive non-small cell lung cancer: An observational real world study.

BACKGROUND: Pralsetinib, a selective RET targeted tyrosine kinase inhibitor (TKI), has been approved for treating locally advanced or metastatic RET fusion-positive NSCLC in adults who have previously received platinum-based chemotherapy in China. METHODS: In this retrospective analysis conducted at Hunan Cancer Hospital in China, we examined 36 patients with advanced NSCLC with RET fusion, who were treated with pralsetinib between January 2021 and December 2023. The study focused on assessing the efficacy (Progression-free survival (PFS) and overall survival (OS)) and safety profile of pralsetinib in these patients. Statistical analyses were conducted using SPSS version 20.0, with a significance level set at p < 0.05. RESULTS: The results revealed that pralsetinib exhibited significant activity in this patient cohort. Kaplan-Meier survival analysis indicated a median PFS of 10.7 months and a median OS of 21.2 months. The overall response rate(ORR) and disease control rate (DCR) was 55.6 % and 72.2 %, respectively. Pralsetinib was generally well tolerated, with most adverse events being mild to moderate (grades 1-2). The most common serious adverse events (≥grade 3) observed were lymphopenia (13.9 %), hypertension (11.1 %), leukopenia (8.3 %), neutropenia (8.3 %), and creatine kinase elevation (8.3 %). CONCLUSION: Pralsetinib demonstrated promising activity in patients with advanced NSCLC harboring RET fusion with a favorable safety profile.

MIG6 loss increased RET inhibitor tolerant persister cells in RET-rearranged non-small cell lung cancer.

Recently approved RET tyrosine kinase inhibitors (TKIs) have shown promising therapeutic effects against RET-rearranged non-small cell lung cancer (NSCLC) or RET-mutated thyroid cancer. However, resistance develops, limiting long-term efficacy. Although many RET-TKI resistance mechanisms, such as secondary mutations in RET or activation of bypass pathways, are known, some primary or acquired resistance mechanisms are unclear. Here, human genome-wide CRISPR/Cas9 screening was performed to identify genes related to drug-tolerant persister cells. Patient-derived cells with RET-fusion were introduced genome-wide sgRNA library and treated with RET-TKI for 9 days, resulting in the discovery of several candidate genes. Knockout of MED12 or MIG6 significantly increased residual drug-tolerant persister cells under RET-TKI treatment. MIG6 loss induced significant EGFR activation even with low concentrations of EGFR ligands and led to resistance to RET-TKIs. EGFR inhibition with afatinib or cetuximab in combination with RET TKIs was effective in addressing drug persistence. By contrast, a KIF5B-RET positive cells established from a RET-rearranged NSCLC patient, showed significant resistance to RET-TKIs and high dependence on EGFR bypass signaling. Consistently, knocking out EGFR or RET led to high sensitivity to RET or EGFR inhibitor respectively. Here, we have provided a comprehensive analysis of adaptive and acquired resistance against RET-rearranged NSCLC.

Lazarus Response to Selpercatinib for Bleeding Colic Metastasis in a Patient With RET Fusion-Positive Pulmonary Sarcomatoid Carcinoma: A Case Report.

In recent years, the widespread use of next-generation sequencing (NGS) allowed clinicians to identify and treat non-small cell lung cancer (NSCLC) efficiently with target therapy. RET inhibitors, like selpercatinib and pralsetinib, for RET rearrangements in lung cancer showed high efficacy and clinical benefit. Nevertheless, to date, the use of molecular-targeted agents has not been tested in all lung cancer subtypes. Indeed, pulmonary sarcomatoid carcinoma (PSC) remains a rare form of NSCLC, unresponsive to standard chemotherapy, and associated with extremely poor prognosis. We report the first case of a patient affected by RET fusion-positive PSC with a bleeding colic metastasis and a consequent poor performance status who achieved a dramatic response to selpercatinib and a remarkable clinico-radiological benefit.

Efficacy of immunotherapy in RET fusion-positive NSCLC: A meta-analysis.

Background: The Rearranged during Transfection (RET) gene represents a rare driver mutation in non-small cell lung cancer (NSCLC) occurring in only 1 %-2 % of cases, with implications in targeted carcinogenesis. Despite the significant efficacy demonstrated by immunotherapy in advanced NSCLC with wild-type driver genes, its validation in RET fusion-positive patients is yet to be established. Objectives: This meta-analysis aims to systematically evaluate the effectiveness of immunotherapy in patients with RET fusion-positive NSCLC. Data sources: and Methods: PubMed and Web of Science databases were systematically searched for relevant studies. Outcomes including objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS), and overall survival (OS) were extracted for further analysis. Results: Ten real-world evidence (RWE) studies involving 7145 patients were enrolled in this meta-analysis. In terms of tumor response, the pooled ORR and DCR were 24.0 % and 61.0 %, respectively. Regarding survival analysis, the pooled median PFS and median OS were 4.17 months [95 % confidence interval (CI): 3.40-5.02) and 17.22 months (95 % CI: 11.58-23.91)], respectively. Subgroup analyses showed that immunotherapies plus chemotherapy were superior to single-immunotherapy in terms of ORR, DCR, and median PFS, which were 43 % (95 % CI: 31%-55 %) vs. 17 % (95 % CI: 11%-25 %), 74 % (95 % CI: 60%-84 %) vs. 45 % (95 % CI: 31%-59 %) and 6.69 months (95 % CI: 4.91-8.93) vs. 2.96 months (95 % CI: 2.25-3.78), respectively. Conclusions: To date, RET fusions appear to be associated with poor response to immunotherapy in NSCLC patients, and immunotherapy combined with chemotherapy seems to offer greater clinical benefits than mono-immunotherapy.

Small cell lung carcinoma with KIF5B-RET fusion partially responded to the 4th-line therapy with anlotinib: A case report.

BACKGROUND: Small cell lung cancer (SCLC) exhibits a pronounced tendency for metastasis and relapse, and the acquisition of resistance to chemotherapy and radiotherapy, leading to complexity in treatment outcomes. It is crucial to tackle these challenges by advancing targeted therapeutic approaches in ongoing research endeavors. Variant RET fusions have been reported in several solid tumors, but are rarely reported in SCLC. CASE SUMMARY: We present the first case of a KIF5B-RET fusion in a 65-year-old male patient with SCLC. To date, the patient has received the 4th line chemotherapy with anlotinib for one year and has shown a sustained favorable partial response. According to the results of next generation sequencing, this SCLC patient harbors the KIF5B-RET fusion, suggesting that RET fusion could serve as a promising molecular target for SCLC treatment. Next-generation sequencing (NGS) plays a critical role in comprehensively assessing the genotype and phenotype of cancer. CONCLUSION: NGS can provide SCLC patients with personalized and targeted therapy options, thereby improving their likelihood of survival.

A Locally Advanced NSCLC Patient Harboring a Rare KIF13A-RET Fusion Benefited from Pralsetinib: A Case Report.

The application of adjuvant treatment has significantly enhanced the survival of patients with resectable non-small cell lung cancer (NSCLC) carrying driver gene mutations. However, adjuvant-targeted therapy remains controversial for some NSCLC patients carrying rare gene mutations such as RET, as there is currently a lack of confirmed randomized controlled trials demonstrating efficacy. In this report, we describe the case of a 58-year-old man with stage IIIA NSCLC who underwent complete lobectomy with selective lymph node dissection. Postoperative next-generation sequencing revealed that the patient harbored a rare KIF13A-RET fusion. The patient elected to receive adjuvant treatment with pralsetinib monotherapy and underwent serial circulating tumor DNA (ctDNA) monitoring after surgery. During follow-up, despite experiencing dose reduction and irregular medication adherence, the patient still achieved a satisfactory disease-free survival (DFS) of 27 months. Furthermore, ctDNA predicted tumor recurrence 4 months earlier than imaging techniques. The addition of bevacizumab to the original regimen upon recurrence continued to be beneficial. Pralsetinib demonstrated promising efficacy as adjuvant therapy, while ctDNA analysis offered a valuable tool for early detection of tumor recurrence. By leveraging targeted therapies and innovative monitoring techniques, we aim to improve outcomes and quality of life for NSCLC patients in the future.

A case of organizing pneumonia in rearranged during transfection fusion-positive lung adenocarcinoma treated with selpercatinib.

Selpercatinib is the first targeted therapy for rearranged during transfection (RET) fusion-positive unresectable non-small-cell lung cancer (NSCLC). The main adverse effects of selpercatinib include hypertension, liver dysfunction, diarrhea, and QT prolongation on electrocardiograms. However, instances of drug-induced interstitial lung disease (DI-ILD) are infrequently reported. We describe the first case of a patient with RET fusion-positive NSCLC treated with selpercatinib who developed DI-ILD, confirmed pathologically. The patient, a 72-year-old woman, initiated selpercatinib treatment following the postoperative recurrence of lung adenocarcinoma. After 15 months of treatment, computed tomography scans revealed multiple infiltrates and ground-glass opacities in both lungs. A thoracoscopic lung biopsy identified organizing pneumonia, attributed to DI-ILD caused by selpercatinib. Although she was asymptomatic, the patient's selpercatinib treatment was discontinued, leading to a gradual improvement in the lung infiltrates. Despite the lack of detailed reports, DI-ILD with selpercatinib represents a potentially serious adverse event and should be approached with caution.

LIBRETTO-431: Confirming the Superiority of Selpercatinib to Chemotherapy and the Lack of Efficacy of Immune Checkpoint Inhibitors in Advanced RET Fusion-Positive (RET+) NSCLC, Another Unique Never-Smoker Predominant Molecular Subtype of NSCLC.

Selpercatinib, a potent and highly selective RET kinase inhibitor with significant CNS activity, has recently gained US approval for the treatment of NSCLC harboring RET fusions (RET+) based on a large-scale single-arm study. The LIBRETTO-431 trial was the global pivotal registration phase 3 trial comparing selpercatinib to platinum-based chemotherapy with or without pembrolizumab as the first-line treatment of patients with advanced RET+ NSCLC. Never-smokers constituted 67.4% of the RET+ NSCLC patients enrolled. KIF5B-RET made up the vast majority (77%) of the RET+ fusion variant with known fusion partner. The results of this study demonstrated significant improvement in progression-free survival (PFS) benefit as well as impressive intracranial disease response in participants treated with selpercatinib as compared to those treated with chemotherapy, with a HR [hazard ratio] of 0.46 (95% CI 0.33-0.70; P < 0.001) for the intention-to-treat (ITT)-pembrolizumab group and HR of 0.46 (95% CI 0.31-0.70, P < 0.001) for the overall ITT-group of patients. The addition of pembrolizumab to platinum/pemetrexed chemotherapy resulted in numerically identical PFS (11.2 months). These results point to selpercatinib's superiority to traditional chemotherapy regimens in the treatment of NSCLC harboring RET fusions and add to literature on the salience of targeted precision oncology and lack of efficacy of immune checkpoint inhibitor in NSCLC patients with never-smoker predominant actionable driver mutations. RET+ NSCLC should be added to the list of molecular subtypes (EGFR+, ALK+, ROS1+) of NSCLC to be excluded in chemoimmunotherapy trial.

Primary Resistance to RET Inhibition in a RET Fusion-Positive Pancreatic Neuroendocrine Carcinoma.

We present a 54-year-old White male with a diagnosis of stage IV pancreatic neuroendocrine carcinoma. Next-generation sequencing of the tumor/blood identified a complex tumor genome, which included a rearranged during transfection (RET) gene fusion. The patient initially received cytotoxic chemotherapy with a significant radiographic response. After 4 cycles of chemotherapy, the patient was transitioned to a clinical trial using selpercatinib, a RET inhibitor, as maintenance therapy. Unfortunately, our patient developed progression of disease at the first treatment monitoring scan. Our patient suffered primary resistance to RET-targeted therapy. Proposed mechanisms of resistance include intrinsic resistance of the nuclear receptor co-activator 4-RET fusion to RET inhibition, the RET fusion representing a passenger alteration to another tumorigenic driver pathway and/or decreased efficacy of RET inhibition after platinum-based chemotherapy. Our patient's clinical course highlights the fact that "actionable" genomic alterations do not always equate to patient benefit.

Cabozantinib Response in a Patient With NSCLC Harboring Both MET Exon 14 Skipping Mutation and Secondary RET Fusion: A Case Report.

MET exon 14 skipping mutation has emerged as a new oncogenic driver in NSCLC with available targeted therapies, including Food and Drug Administration-approved inhibitors capmatinib and tepotinib. Potential resistance mechanisms are beginning to be described and include several on-target and off-target mutations. Here, we report an emergent secondary RET fusion in a patient with a primary MET exon 14 skipping mutation that progressed on capmatinib after the initial response. Subsequently, this patient received both a RET inhibitor (selpercatinib) followed by another MET-targeted treatment (tepotinib) without clinical benefit. Thereafter, cabozantinib, a multikinase inhibitor with activity against RET and MET was started with a rapid clinical and radiologic benefit.

Concurrent KRAS p.G12C mutation and ANK3::RET fusion in a patient with metastatic colorectal cancer: a case report.

BACKGROUND: Colorectal cancer (CRC) frequently involves mutations in the KRAS gene, impacting therapeutic strategies and prognosis. The occurrence of KRAS mutations typically precludes the presence of RET fusions, with current medical literature suggesting a mutual exclusivity between these two genetic alterations. We present a unique case that challenges this notion. CASE PRESENTATION: An 85-year-old female with metastatic CRC was found to have a combination of genetic anomalies that is to the best of our knowledge not yet described in the medical literature: a KRAS p.G12C mutation, associated with oncogenesis and treatment resistance, and an ANK3::RET fusion, an infrequent but targetable mutation in CRC. This molecular profile was uncovered through comprehensive genomic sequencing after the patient experienced metachronous tumor dissemination. The presence of both genetic events complicates the treatment approach. CONCLUSIONS: The identification of both a KRAS p.G12C mutation and an ANK3::RET fusion in the same CRC patient adds a new layer to the oncogenic landscape and treatment considerations for CRC. It highlights the intricate decision-making required in the era of precision medicine, where targeted therapies must be carefully chosen and potentially combined to combat complex genetic profiles. The case emphasizes the urgency of investigating the clinical effects of concurrent or sequential use of KRAS p.G12C and RET inhibitors to inform future therapeutic guidelines and improve patient outcomes in similar cases.

Multicenter evaluation of an automated, multiplex, RNA-based molecular assay for detection of ALK, ROS1, RET fusions and MET exon 14 skipping in NSCLC.

The current study assessed the performance of the fully automated RT-PCR-based Idylla™ GeneFusion Assay, which simultaneously covers the advanced non-small cell lung carcinoma (aNSCLC) actionable ALK, ROS1, RET, and MET exon 14 rearrangements, in a routine clinical setting involving 12 European clinical centers. The Idylla™ GeneFusion Assay detects fusions using fusion-specific as well as expression imbalance detection, the latter enabling detection of uncommon fusions not covered by fusion-specific assays. In total, 326 archival aNSCLC formalin-fixed paraffin-embedded (FFPE) samples were included of which 44% were resected specimen, 46% tissue biopsies, and 9% cytological specimen. With a total of 179 biomarker-positive cases (i.e., 85 ALK, 33 ROS1, 20 RET fusions and 41 MET exon 14 skipping), this is one of the largest fusion-positive datasets ever tested. The results of the Idylla™ GeneFusion Assay were compared with earlier results of routine reference technologies including fluorescence in situ hybridization, immunohistochemistry, reverse-transcription polymerase chain reaction, and next-generation sequencing, establishing a high sensitivity/specificity of 96.1%/99.6% for ALK, 96.7%/99.0% for ROS1, 100%/99.3% for RET fusion, and 92.5%/99.6% for MET exon 14 skipping, and a low failure rate (0.9%). The Idylla™ GeneFusion Assay was found to be a reliable, sensitive, and specific tool for routine detection of ALK, ROS1, RET fusions and MET exon 14 skipping. Given its short turnaround time of about 3 h, it is a time-efficient upfront screening tool in FFPE samples, supporting rapid clinical decision making. Moreover, expression-imbalance-based detection of potentially novel fusions may be easily verified with other routine technologies without delaying treatment initiation.

Case report: First evidence of impressive efficacy of modulated dose selpercatinib in a young Caucasian with ANK3-RET fusion-positive NSCLC.

Over the past decade, molecular characterization has led to change the management of advanced non-small cell lung cancer (NSCLC) harboring driver mutations. Rearranged during transfection (RET) gene fusions, occurring in 1% to 2% of NSCLC, have emerged as an oncogenic druggable target. Systemic targeted therapies with highly selective RET inhibitors (RETi), selpercatinib and pralsetinib, represent a recent clinical breakthrough. While the development of RETi has improved survival, with their increasing use, it is crucial to be aware of the risks of rare but serious adverse events (AEs). A particular challenge for clinicians in applying targeted therapies is not only diagnosing but also interpreting rare mutations. Herein, we report a case of a 43-year-old Caucasian advanced NSCLC patient diagnosed with a rare RET gene fusion, ANK3::RET, identified with Next Generation Sequencing (NGS). Selpercatinib has been initiated at the recommended initial dose after one incomplete chemotherapy cycle due to a severe infusion reaction, but it subsequently required a dose adjustment following grade 3 (G3) AEs. During treatment, we used a particular selpercatinib dosage (160 mg in the morning and 80 mg in the evening) with good tolerance and without compromising effectiveness. Our finding broadens the range of RET fusion types in not-Asian NSCLC. To the best of our knowledge, our case demonstrates, for the first time, a clinical and radiological response to frontline highly selective RETi selpercatinib, expanding the spectrum of potential oncogenic RET fusion partners in newly diagnosed NSCLC patients. Furthermore, to our knowledge, this is the first case describing a RET fusion-positive (RET+) NSCLC patient treated with a modified selpercatinib dosage outside the drug data sheet and demonstrating a safe and effective use.

Real-world outcomes of chemoimmunotherapy and selective RET inhibitors in Chinese patients with RET fusion-positive non-small cell lung cancer.

Background: Rearranged during transfection (RET) gene fusion is a target for non-small cell lung cancer (NSCLC) treatment, and RET inhibitors are approved for advanced NSCLC. The role of immune checkpoint inhibitors (ICIs) in RET fusion-positive NSCLC remains controversial. This retrospective study analyzed the efficacy of ICIs and RET inhibitors in Chinese patients with RET fusion-positive NSCLC. Methods: Data from patients diagnosed with advanced NSCLC harboring RET fusion from Jan 2017 to Sep 2021 were analyzed. Clinicopathological characteristics and outcomes of ICIs and RET inhibitors treatments were collected. Results: Seventy-five patients with RET fusion-positive advanced NSCLC were identified. The median age of patients was 57 years, half of the patients were female (50.3%), and most were non-smokers or light smokers (72%). Of the cancer types diagnosed in study patients, the KIF5B-RET fusion subtype accounted for 73.3% (55/75), twelve patients (16%) had CCDC6-RET fusion, and three (4%) had NCOA4-RET fusion. Sixteen patients were treated with ICIs. In previously untreated patients, we observed an objective response rate (ORR) of 71.4% and median progression free survival (PFS) of 7.5 months in seven assessable patients. Of four patients with PD-L1 overexpression (>50%) one received pembrolizumab and the other three patients received pemetrexed, carboplatin, and pembrolizumab or camrelizumab. In these patients, the ORR was 75% and disease control rate was 100%. Fifteen patients received selective RET inhibitors (pralsetinib and selpercatinib), resulting in an ORR of 53.3% (8/15) and median PFS of 10.0 months (95% CI 5.2-14.9). Conclusions: ICIs for PD-L overexpression and treatment naive patients offer comparable benefits for RET fusion-positive NSCLC, warranting further investigation.

Impact of tissue-agnostic approvals on management of primary brain tumors.

Novel tissue-agnostic therapeutics targeting driver mutations in tumor cells have been recently approved by FDA, driven by basket trials that have demonstrated their efficacy and safety across diverse tumor histology. However, the relative rarity of primary brain tumors (PBTs) has limited their representation in early trials of tissue-agnostic medications. Thus, consensus continues to evolve regarding utility of tissue-agnostic medications in routine practice for PBTs, a diverse group of neoplasms characterized by limited treatment options and unfavorable prognoses. We describe current and potential impact of tissue-agnostic approvals on management of PBTs. We discuss data from clinical trials for PBTs regarding tissue-agnostic targets, including BRAFV600E, neurotrophic tyrosine receptor kinase (NTRK) fusions, microsatellite instability-high (MSI-High), mismatch repair deficiency (dMMR), and high tumor mutational burden (TMB-H), in context of challenges in managing PBTs. Described are additional tissue-agnostic targets that hold promise for benefiting patients with PBTs, including RET fusion, fibroblast growth factor receptor (FGFR), ERBB2/HER2, and KRASG12C, and TP53Y220C.

Pralsetinib in patients with RET fusion-positive non-small-cell lung cancer: A plain language summary of the ARROW study.

WHAT IS THIS SUMMARY ABOUT?: This is a summary of a research study called ARROW, which tested a medicine called pralsetinib in patients with non-small cell lung cancer (NSCLC), thyroid cancer, and other advanced solid tumours caused by a change in a gene called RET. For the purposes of this summary, only patients with NSCLC with a change in RET called fusion (RET fusion+) are highlighted. WHAT WERE THE RESULTS?: In total, 281 patients with RET fusion+ NSCLC had taken part in this study across the USA, Europe, and Asia. Patients were asked to take four pills (adding up to 400 mg) of pralsetinib each day and were checked for any changes in their tumours, as well as for any side effects. After an average of 8 months of treatment with pralsetinib, 72% of previously untreated patients and 59% of patients who had previously received chemotherapy had considerable shrinkage of their tumours. Among 10 patients with tumours which had spread to the brain (all of whom had received previous treatments), 70% had their tumours shrink greatly in the brain after treatment with pralsetinib. On average, patients lived with little to no tumour growth for 16 months. In previously untreated patients, the most common severe side effects that were considered related to pralsetinib treatment were decreased white blood cells (neutrophils and lymphocytes), increased blood pressure, and an increase in a blood protein called creatine phosphokinase. In previously treated patients, the severe side effects were decreased white blood cells (neutrophils, lymphocytes, and leukocytes), increased blood pressure, and low levels of red blood cells. In both untreated and previously treated patients, the most common severe side effects that required hospital attention were lung inflammation/swelling causing shortness of breath (pneumonitis) and lung infection (pneumonia). WHAT DO THE RESULTS MEAN?: Overall, the ARROW study showed that pralsetinib was effective in shrinking tumours in patients with RET fusion+ NSCLC regardless of previous treatment history. The recorded side effects were expected in patients receiving this type of medicine. Clinical Trial Registration: NCT03037385 (ARROW) (ClinicalTrials.gov).

Comprehensive next-generation sequencing reveals double primary colorectal carcinoma missed by diagnostic imaging: A case report.

BACKGROUND: Multiple primary colorectal carcinoma (MPCC) is a rare clinical disease, which is challenging to differentiate from metastatic disease using histopathological methods. Next-generation sequencing (NGS) has been employed to identify multiple primary cancers. CASE SUMMARY: This study a rare case of a 63-year-old male patient diagnosed with MPCC by targeted NGS, which was initially missed by radiological evaluation. The patient was found to have two tumors located on the surface of the colorectum which had distinct genomic alterations. Based on wild-type KRAS detected in the unresected tumor, the patient benefited from the epidermal growth factor receptor (EGFR) inhibitor cetuximab treatment, but developed novel mutations including KIF5B-RET fusion, which provides a possible resistance mechanism to anti-EGFR therapy. CONCLUSION: Our case highlights the necessity of using genetic testing for primary tumor diagnosis and the application of serial plasma circulating tumor DNA profiling for dynamic disease monitoring.