Whole exome sequencing (WES) analysis of transformed small cell lung cancer (SCLC) from lung adenocarcinoma (LUAD)

Comprehensive molecular and clinical insights into non-small cell lung cancer transformation to small cell lung cancer with an illustrative case report

Histologic transformation to small cell lung cancer (tSCLC) is a rare but increasingly recognised mechanism of acquired resistance to tyrosine kinase inhibitors (TKI) in patients with epidermal growth factor receptor (EGFR)-positive non-small cell lung cancer (NSCLC). Beyond its acknowledged role in TKI resistance, histologic transformation to SCLC might be an important, yet under-recognised, mechanism of resistance in NSCLC treated with immunotherapy. Our review identified 32 studies that investigated tSCLC development in patients with EGFR-mutated NSCLC treated with TKI therapy and 16 case reports of patients treated with immunotherapy. It revealed the rarity of tSCLC, with a predominance of EGFR exon 19 mutations and limited therapeutic options and outcomes. Across all analysed studies in EGFR-mutated NSCLC treated with TKI therapy, the median time to tSCLC development was ∼17 months, with a median overall survival of 10 months. Histologic transformation of EGFR-mutated NSCLC to SCLC is a rare, but challenging clinical problem with a poor prognosis. A small number of documented cases of tSCLC after immunotherapy highlight the need for rebiopsies at progression to diagnose this potential resistance mechanism. Further research is needed to better understand the mechanisms underlying this phenomenon and to develop more effective treatment strategies for patients with tSCLC.

Establishment and characterization of BMC-PDC-019: a novel patient-derived cell line of EGFR-mutant pulmonary adenocarcinoma transformed into small-cell lung cancer

Transformed small-cell lung cancer (tSCLC) from EGFR-mutant adenocarcinoma is a rare and aggressive form of lung cancer that can occur when the tumor develops resistance to EGFR targeted therapy and the cancer cells acquire additional genomic alterations that cause them to transform into SCLC. Treatment for tSCLC has not been established yet, and chemotherapy regimens for de novo SCLC are mostly recommended. However, these treatments showed disappointing outcome, and novel anti-cancer agents and immunological approaches are currently being developed. The patient-derived cell line is a critical tool for pre-clinical and translational research, but cell line models for tSCLC are not publicly available from cell banks. The aim of this study was to establish and characterize a novel cell line for tSCLC. Using a lymph-node biopsy tissue from a 58-year-old female patient, whose tumor was EGFR-mutant lung adenocarcinoma progressed on afatinib, we successfully established a cell line, named BMC-PDC-019. The tumor sample and cell line showed a typical expression of SCLC markers, such as CD56 and synaptophysin. The population doubling-time of BMC-PDC-019 cells was 48 h. We examined a range of proliferation-inhibiting effects of anti-cancer drugs currently used for de novo SCLC, using BMC-PDC-019 cells. We concluded that BMC-PDC-019 would be a useful tool for pre-clinical and translational research.

Histological transformation into SCLC: An important resistance mechanism of NSCLC upon immunotherapy

The phenomenon of histological transformation has been widely reported in advanced non-small cell lung cancer (NSCLC) with EGFR mutations following the failure of EGFR-TKI treatment. Recent evidence suggests that similar histological changes can also occur in advanced NSCLC without driver gene mutations after developing resistance to immunotherapy. In this review, it was found that 66.7% of cases with immunotherapy-induced histological transformation were classified as lung squamous cell carcinoma (LSCC), while histological conversion into lung adenocarcinoma (LUAD) without EGFR or ALK gene mutations has rarely been reported. There have been sporadic reports on the occurrence of mutual transformation between LUAD and LSCC. The histological conversion from NSCLC into small cell lung cancer (SCLC) appears to be significantly underestimated, likely due to the infrequency of re-biopsy following the development of immunotherapy resistance. Several studies have reported a close association between the transformation and mutations at TP53 and the RB1 splice site, as well as the loss of an FBXW7 mutation. However, the exact mechanisms underlying this conversion remain unclear. Currently, there is a lack of guidelines for the management of transformed SCLC from NSCLC following immunotherapy, with chemotherapy being the most commonly employed treatment approach.

Expression of EGFR-mutant proteins and genomic evolution in EGFR-mutant transformed small cell lung cancer

Background

The transformation of epidermal growth factor receptor (EGFR)-mutant lung adenocarcinoma (LUAD) into small cell lung cancer (SCLC) accounts for 3-14% of the resistance mechanism to EGFR tyrosine kinase inhibitors (TKIs). At present, there is no relevant research to explore the dynamic expression of EGFR-mutant proteins and genomic evolution in EGFR-mutant transformed SCLC/neuroendocrine carcinoma (NEC).

Methods

Genetic analysis and protein level analysis by next-generation sequencing (NGS), Whole-exome sequencing (WES) and immunohistochemistry were performed to explore expression of EGFR-mutant proteins and genomic evolution in EGFR-mutant transformed SCLC. The research used three patient-derived organoids (PDOs) to explore the efficacy of combo [chemotherapy (chemo) plus TKI or bevacizumab] treatment. According to the subsequent treatment regimens after SCLC/NEC transformation, 35 patients were divided into chemo (n=21) and combo (n=14) groups.

Results

EGFR L858R and EGFR E746-750 del protein expression by immunohistochemistry was 80.0% (4/5) and 100% (6/6), respectively (P=0.455) in initially-transformed tissues. Meanwhile, EGFR-mutant proteins were expressed in 85.7% (6/7) of dynamic rebiopsy tissues or effusion samples after the first transformation. Then, by the pathway enrichment analysis of tissue and plasma NGS, the EGFR-related pathways were still activated after SCLC/NEC transformation. Moreover, WES analysis revealed that transformed SCLC shared a common clonal origin from the baseline LUAD. The drug sensitivity of three PDOs demonstrated potent anti-cancer activity of EGFR-TKIs plus chemo, compared with chemo or TKI alone. There were significant differences in objective response rate (ORR) between the combo and chemo groups [42.9 % vs. 4.8%, P=0.010, 95% confidence interval (CI): 1.5-145.2]. Furthermore, the median post-transformation progression-free survival (pPFS) was significantly prolonged in the combo group, with 5.4 (95% CI: 3.4-7.4) versus 3.5 (95% CI: 2.7-4.3, P=0.012) months.

Conclusions

EGFR 19del or L858R-mutant proteins could be constantly expressed, and EGFR pathway still existed in EGFR-mutant transformed SCLC/NEC with a common clonal origin from the baseline LUAD. Taking together, these molecular characteristics potentially favored clinical efficacy in transformed SCLC/NEC treated with the combo regimen.

Advances in novel strategies for isolation, characterization, and analysis of CTCs and ctDNA

Over the past decade, the detection and analysis of liquid biopsy biomarkers such as circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA) have advanced significantly. They have received recognition for their clinical usefulness in detecting cancer at an early stage, monitoring disease, and evaluating treatment response. The emergence of liquid biopsy has been a helpful development, as it offers a minimally invasive, rapid, real-time monitoring, and possible alternative to traditional tissue biopsies. In resource-limited settings, the ideal platform for liquid biopsy should not only extract more CTCs or ctDNA from a minimal sample volume but also accurately represent the molecular heterogeneity of the patient's disease. This review covers novel strategies and advancements in CTC and ctDNA-based liquid biopsy platforms, including microfluidic applications and comprehensive analysis of molecular complexity. We discuss these systems' operational principles and performance efficiencies, as well as future opportunities and challenges for their implementation in clinical settings. In addition, we emphasize the importance of integrated platforms that incorporate machine learning and artificial intelligence in accurate liquid biopsy detection systems, which can greatly improve cancer management and enable precision diagnostics.

Integrative Analysis of a Large Real-World Cohort of Small Cell Lung Cancer Identifies Distinct Genetic Subtypes and Insights into Histologic Transformation

Small cell lung cancer (SCLC) is a recalcitrant neuroendocrine carcinoma with dismal survival outcomes. A major barrier in the field has been the relative paucity of human tumors studied. Here we provide an integrated analysis of 3,600 "real-world" SCLC cases. This large cohort allowed us to identify new recurrent alterations and genetic subtypes, including STK11-mutant tumors (1.7%) and TP53/RB1 wild-type tumors (5.5%), as well as rare cases that were human papillomavirus-positive. In our cohort, gene amplifications on 4q12 are associated with increased overall survival, whereas CCNE1 amplification is associated with decreased overall survival. We also identify more frequent alterations in the PTEN pathway in brain metastases. Finally, profiling cases of SCLC containing oncogenic drivers typically associated with NSCLC demonstrates that SCLC transformation may occur across multiple distinct molecular cohorts of NSCLC. These novel and unsuspected genetic features of SCLC may help personalize treatment approaches for this fatal form of cancer.

SIGNIFICANCE

Minimal changes in therapy and survival outcomes have occurred in SCLC for the past four decades. The identification of new genetic subtypes and novel recurrent mutations as well as an improved understanding of the mechanisms of transformation to SCLC from NSCLC may guide the development of personalized therapies for subsets of patients with SCLC. This article is highlighted in the In This Issue feature, p. 1501.

Etoposide/platinum plus anlotinib for patients with transformed small-cell lung cancer from EGFR-mutant lung adenocarcinoma after EGFR-TKI resistance: a retrospective and observational study

Objective

The histological conversion of lung adenocarcinoma (LUAD) into small-cell lung cancer (SCLC) is an important resistance mechanism for epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI)-resistant LUAD. Anlotinib has been recommended as the third-line treatment for SCLC patients. The efficacy of etoposide/platinum (EP) as the main treatment is very limited for patients with transformed SCLC. However, little is known about EP plus anlotinib for transformed SCLC. The present study retrospectively explored the clinical response to EP combined with anlotinib in patients with transformed SCLC from LUAD after EGFR-TKI failure.

Methods

A total of 10 patients who underwent SCLC transformation from EGFR-TKI-resistant LUAD were retrospectively reviewed from September 1, 2019, to December 31, 2022, in three regional hospitals. All of the patients were treated with the combination regimen of EP and anlotinib for four to six cycles, followed by anlotinib maintenance therapy. The clinical efficacy indices including objective response rate (ORR), disease control rate (DCR), median progression-free survival (mPFS), median overall survival (mOS), and toxicities were evaluated.

Results

The median time from EGFR-TKI treatment to SCLC conversion was 20.1 ± 2.76 months (17-24 months). Genetic examination after transformation showed that 90% of the patients retained their original EGFR gene mutations. Additional driver genes were found, including BRAF mutation (10%), PIK3CA mutation (20%), RB1 loss (50%), and TP53 mutation (60%). The ORR and DCR were 80% and 100%, respectively. The mPFS was 9.0 months (95% CI, 7.9-10.1 months), and the mOS was 14.0 months (95% CI, 12.0-15.9 months). Less than 10% of grade 3 toxicities were observed, and no grade 4 toxicity and death events were reported.

Conclusion

The EP plus anlotinib regimen appears to be a promising and safe strategy in transformed SCLC patients after EGFR-TKI resistance, which warrants further investigation.

Current Knowledge of Small Cell Lung Cancer Transformation from Non-Small Cell Lung Cancer

Lung cancer is the leading cause of cancer related death, and is divided into two major histological subtypes, non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). Histological transformation from NSCLC to SCLC has been reported as a mechanism of treatment resistance in patients who received tyrosine kinase inhibitors (TKIs) targeting EGFR, ALK and ROS1 or immunotherapies. The transformed histology could be due to therapy-induced lineage plasticity or clonal selection of pre-existing SCLC cells. Evidence supporting either mechanism exist in the literature. Here, we discuss potential mechanisms of transformation and review the current knowledge about cell of origin of NSCLC and SCLC. In addition, we summarize genomic alterations that are frequently observed in both "De novo" and transformed SCLC, such as TP53, RB1 and PIK3CA. We also discuss treatment options for transformed SCLC, including chemotherapy, radiotherapy, TKIs, immunotherapy and anti-angiogenic agents.

Evolution of small cell lung cancer tumor mutation: from molecular mechanisms to novel viewpoints

Small cell lung cancer (SCLC) is a clinically common malignant tumor originating from the lung neuroendocrine stem cells, which has a poor prognosis and accounts for approximately 15% of all lung cancer cases. However, research on its treatment has been slow, and the 5-year survival rate of patients with SCLC has been < 5% for many years. In recent years, the development and popularization of gene sequencing technology have facilitated the understanding of the gene mutation landscape and tumor evolution of SCLC, thereby leading to a more accurate prediction of the prognosis of SCLC and the development of individualized treatment. In this review, we aimed to discuss the mutation evolution of SCLC from the perspective of a tumor evolution theory and described the sequence of mutation evolution in the occurrence and development of SCLC. In addition, we summarized the existing whole-exome sequencing (WES) data of SCLC cases at our center along with relevant publications on sequencing. Thereafter, we discuss the role of different mutated pathways in the occurrence of SCLC to predict its prognosis more accurately and summarized individualized treatment strategies.

Sequential small cell transformation and T790M mutation in an epidermal growth factor-mutant lung adenocarcinoma: A rare occurrence with significant management implications

BACKGROUND

Epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI) resistance may be acquired via genotypic and/or phenotypic transformations. Herein, we report an extremely uncommon case with sequential small cell transformation and EGFR T790M mutation, in an elderly female with EGFR exon 21 L858R-mutant lung adenocarcinoma, following treatment with a first-generation EGFR-TKI.

CASE

A 67-year-old female, never-smoker, presented with cough and dyspnoea of two months' duration. Computerized tomography revealed a 39mm lesion in the upper lobe of right lung with pleural effusion. Pleural fluid cytology revealed metastatic lung adenocarcinoma and EGFR testing revealed exon 21 L858R mutation. She was started on gefitinib. After a progression-free survival of 31 months, she presented with disease progression and multiple extra-thoracic metastases. Fine needle aspiration cytology from a chest wall lesion revealed metastatic small cell carcinoma. EGFR testing on this aspirate revealed persistent L858R mutation only. In view of small cell transformation, chemotherapy (etoposide and carboplatin) was administered. After four months, ascitic fluid cytology revealed metastatic adenocarcinoma with persistent L858R mutation and an acquired T790M mutation (both detected on liquid biopsy as well) indicating amplification of the adenocarcinoma clone and regression of the small cell carcinoma clone. She was then initiated on osimertinib.

CONCLUSIONS

The index case highlights the significance of serial EGFR genotyping along with repeated tissue and/or blood sampling for the prompt detection of genetic and phenotypic resistance mechanisms to EGFR-TKIs. Furthermore, it lends evidence to the upfront treatment approaches targeting the heterogeneity of acquired EGFR-TKI resistance mechanisms.

Small cell lung cancer transformation: From pathogenesis to treatment

Small cell lung cancer (SCLC) is a type of neuroendocrine tumor with high malignancy and poor prognosis. Besides the de novo SCLC, there is transformed SCLC, which has similar characteristics of pathological morphology, molecular characteristics, clinical manifestations and drug sensitivity. However, de novo SCLC and transformed SCLC have different pathogenesis and tumor microenvironment. SCLC transformation is one of the mechanisms of resistance to chemotherapy, immunotherapy, and targeted therapy in NSCLC. Two hypotheses have been used to explain the pathogenesis of SCLC transformation. Although SCLC transformation is not common in clinical practice, it has been repeatedly identified in many small patient series and case reports. It usually occurs in epidermal growth factor receptor (EGFR) mutant lung adenocarcinoma after treatment with tyrosine kinase inhibitors (TKIs). SCLC transformation can also occur in anaplastic lymphoma kinase (ALK)-positive lung cancer after treatment with ALK inhibitors and in wild-type EGFR or ALK NSCLC treated with immunotherapy. Chemotherapy was previously used to treat transformed SCLC, yet it is associated with an unsatisfactory prognosis. We comprehensively review the advancements in transformed SCLC, including clinical and pathological characteristics, and the potential effective treatment after SCLC transformation, aiming to give a better understanding of transformed SCLC and provide support for clinical uses.

Outcomes in Patients With Lung Adenocarcinoma With Transformation to Small Cell Lung Cancer After EGFR Tyrosine Kinase Inhibitors Resistance: A Systematic Review and Pooled Analysis

Background

Lung adenocarcinoma can transform into small-cell lung cancer (SCLC) when resistance to tyrosine kinase inhibitors (TKIs) develops. Approximately 3% to 10% of epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancer (NSCLC) could transform to SCLC. This phenomenon has been described in several case reports and small patient series. However, the characteristics and treatment outcomes of this population have not been comprehensively reported, and their clinical course is poorly characterized.

Methods

We performed a systematic review of the published literature to summarize the clinical and pathological features and prognosis of the reported cases and analyzed the demographics, disease features, and outcomes.

Results

A total of 72 patients (50 females and 22 males) initially diagnosed with lung adenocarcinoma were included. EGFR mutations included 19-deletion (75%), L858R (22%), and G719X (3%). All patients received EGFR-TKIs before SCLC transformation. The median time from diagnosis to transformation was 20.5 months (95% CI, 15.45 to 26.55 months). Of the 67 patients with post-translational gene test results, 58 maintained their EGFR mutation, and only 1 of 18 with prior T790M positivity retained T790M mutation. After the pathological transformation, both conventional chemotherapy regimen and chemotherapy combined targeted therapy yielded high response rates. The disease control rate of first-line therapy after transformation was 76%, while the objective response rate was 48%. The median overall survival (OS) since diagnosis was 27 months (95% CI, 22.90 to 31.10 months), whereas median OS since SCLC transformation was 8.5 months (95% CI, 5.50 to 11.60 months).

Conclusion

The prognosis of transformed SCLC is worse than primary SCLC. The response rate to conventional chemotherapy was high. However, the progression-free survival and OS after transformation were short and the prognosis was poor with first-line therapies. New therapies are needed in the management of transformed SCLC.

Clinical features and prognostic factors of combined small cell lung cancer: development and validation of a nomogram based on the SEER database

Background

Combined small-cell lung cancer (CSCLC) refers to the simultaneous presence of small cell lung cancer (SCLC) and any subtype of the non-small cell lung cancer (NSCLC). This study aimed to explore the prognosis of CSCLC, NSCLC, and pure SCLC patients, and to develop a nomogram to estimate the overall survival (OS) for CSCLC patients.

Methods

Patients diagnosed with NSCLC, CSCLC, and pure SCLC between 2004 and 2015 were identified from the Surveillance Epidemiology and End Results (SEER) database. Survival analyses were performed by using the Kaplan Meier curves and Cox proportional hazards regression. All CSCLC patients were randomly split 7:3 into training and validation sets. A nomogram was developed by integrating all independent predictors for OS. The performance of the nomogram was determined by discrimination, calibration ability, clinical usefulness, and risk stratification ability.

Results

A total of 326,695 lung cancer patients, including 871 with CSCLC, 280,391 with NSCLC, and 45,433 with pure SCLC were enrolled. CSCLC was associated with worse survival compared with NSCLC both in the unmatched and matched cohorts. However, compared to pure SCLC, CSCLC was associated with significantly better survival in the unmatched cohorts only, while showed marginally non-significantly better survival after propensity score matching (PSM). For CSCLC, a nomogram was constructed for the 6-month, 1-year, and 3-year OS prediction by combining the independent risk factors, including age, gender, tumor, node, and metastasis stage, surgery, and chemotherapy. The nomogram showed good discrimination and calibration both in the training and validation sets, and better performance than the tumor-node-metastasis staging system. Risk stratification analysis indicated that the nomogram scores efficiently divided CSCLC patients into low-, intermediate-, and high-risk groups (P<0.001).

Conclusions

CSCLC patients presented a significantly worse prognosis than patients with NSCLC, but comparable prognosis when compared with pure SCLC patients in the matched cohorts. In addition, we developed and validated a nomogram for predicting the 6-month, 1-year, and 3-year OS in CSCLC patients.

Challenge and countermeasures for EGFR targeted therapy in non-small cell lung cancer

Lung cancer causes the highest mortality compared to other cancers in the world according to the latest WHO reports. Non-small cell lung cancer (NSCLC) contributes about 85% of total lung cancer cases. An extensive number of risk factors are attributed to the progression of lung cancer. Epidermal growth factor receptor (EGFR), one of the most frequently mutant driver genes, is closely involved in the development of lung cancer through regulation of the PI3K/AKT and MAPK pathways. As a representative of precision medicine, EGFR-tyrosine kinase inhibitors (TKIs) targeted therapy significantly relieves the development of activating mutant EGFR-driven NSCLC. However, treatment with TKIs facilitates the emergence of acquired resistance that continues to pose a significant hurdle with respect to EGFR targeted therapy. In this review, the development of current approved EGFR-TKIs as well as the related supporting clinical trials are summarized and discussed. Mechanisms of action and resistance were addressed respectively, which serve as important guides to understanding acquired resistance. We also explored the corresponding combination treatment options according to different resistance mechanisms. Future challenges include more comprehensive characterization of unclear resistance mechanisms in different populations and the development of more efficient and precision synthetic therapeutic strategies.

[Research Advances on Transformation to Small Cell Lung Cancer]

小细胞肺癌（small cell lung cancer, SCLC）转化是非小细胞肺癌尤其是表皮生长因子受体（epidermal growth factor receptor, EGFR）突变患者的重要耐药机制之一。目前发现转化性SCLC具有与原发性SCLC相似的临床特征，对化疗短期有效，中位生存期仅1年左右。RB1缺失、体细胞拷贝数改变与SCLC转化有关，但发生SCLC转化的确切分子机制仍不完全清楚。转化性SCLC的治疗也面临巨大的挑战，针对SCLC的化疗方案是目前的主要治疗选择，联合治疗、局部治疗以及预防SCLC转化的策略也在探索。本文将转化性SCLC的临床特征、分子机制和治疗选择进行综述。