A patient with simultaneously appearing adenocarcinoma and small-cell lung carcinoma harbouring an identical EGFR exon 19 mutation

Morphologic-Molecular Transformation of Oncogene Addicted Non-Small Cell Lung Cancer

Patients with non-small cell lung cancer, especially adenocarcinomas, harbour at least one oncogenic driver mutation that can potentially be a target for therapy. Treatments of these oncogene-addicted tumours, such as the use of tyrosine kinase inhibitors (TKIs) of mutated epidermal growth factor receptor, have dramatically improved the outcome of patients. However, some patients may acquire resistance to treatment early on after starting a targeted therapy. Transformations to other histotypes—small cell lung carcinoma, large cell neuroendocrine carcinoma, squamous cell carcinoma, and sarcomatoid carcinoma—have been increasingly recognised as important mechanisms of resistance and are increasingly becoming a topic of interest for all specialists involved in the diagnosis, management, and care of these patients. This article, after examining the most used TKI agents and their main biological activities, discusses histological and molecular transformations with an up-to-date review of all previous cases published in the field. Liquid biopsy and future research directions are also briefly discussed to offer the reader a complete and up-to-date overview of the topic.

KRAS: A Druggable Target in Colon Cancer Patients

Mutations in KRAS are among the most frequent aberrations in cancer, including colon cancer. KRAS direct targeting is daunting due to KRAS protein resistance to small molecule inhibition. Moreover, its elevated affinity to cellular guanosine triphosphate (GTP) has made the design of specific drugs challenging. Indeed, KRAS was considered ‘undruggable’. KRASG12C is the most commonly mutated variant of KRAS in non-small cell lung cancer. Currently, the achievements obtained with covalent inhibitors of this variant have given the possibility to assess the best therapeutic approach to KRAS-driven tumors. Mutation-related biochemical assets and the tissue of origin are expected to influence responses to treatment. Further attempts to obtain mutant-specific KRAS (KRASG12C) switch-II covalent inhibitors are ongoing and the results are promising. Drugs targeted to block KRAS effector pathways could be combined with direct KRAS inhibitors, immunotherapy or T cell-targeting approaches in KRAS-mutant tumors. The development of valuable combination regimens will be essential against potential mechanisms of resistance that may arise during treatment.

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.

Pathological transition as the arising mechanism for drug resistance in lung cancer

Despite the tremendous efforts for improving therapeutics of lung cancer patients, its prognosis remains disappointing. This can be largely attributed to the lack of comprehensive understanding of drug resistance leading to insufficient development of effective therapeutics in clinic. Based on the current progresses of lung cancer research, we classify drug resistance mechanisms into three different levels: molecular, cellular and pathological level. All these three levels have significantly contributed to the acquisition and evolution of drug resistance in clinic. Our understanding on drug resistance mechanisms has begun to change the way of clinical practice and improve patient prognosis. In this review, we focus on discussing the pathological changes linking to drug resistance as this has been largely overlooked in the past decades.

Transformation of lung adenocarcinoma to small cell lung carcinoma in the setting of tyrosine kinase inhibitor therapy: Cytological approach of a clinically challenging phenomenon

Lung adenocarcinoma transformation into small cell lung carcinoma is a well-established phenomenon. Several reports and studies have been published, describing the clinical and pathological clues to detect this transformation. This article will discuss the cytological aspect of this entity, highlighting pertinent features, to bring more attention to the existence of this transformation into the cytopathology practice.

Role of Cytomorphology in the Era of Liquid Biopsy

In the late stages of non-small cell lung cancer, the detection of sensitizing mutations of the epidermal growth factor receptor (EGFR) is mandatory to select patients' treatment with first- or second-generation tyrosine kinase inhibitors (TKIs). In patients showing progressive disease, the assessment of the EGFR exon 20 resistance point mutation p.T790M is required for third-generation TKI administration. However, molecular analysis does not capture all the different mechanisms of resistance against these molecules. A variety of morphological changes associated with acquired resistance have also been described. Since an altered morphology may be the only clue to acquired resistance, cytopathology still plays a relevant role in this setting. In this comprehensive review, we have focused on the relevance of squamous cell carcinoma, small cell lung cancer and large-cell neuroendocrine carcinoma transitions from adenocarcinoma resistant to TKIs.

Histologic transformation of non-small-cell lung cancer in brain metastases

BACKGROUND

Treatment strategies differ substantially for small-cell lung cancer (SCLC), adenocarcinoma and squamous-cell cancer (SCC). Therefore, it is of important significance to identify histologic transformation. There are no reports on histologic transformation in brain metastases (BM) to date. The aim of this study was to analyze the histologic transformation in BM for the first time.

METHODS

Medical records were reviewed and patients with both resected BM and primary tumors were examined retrospectively. The histologic diagnosis was confirmed by H&E staining, and additional diagnostic immunohistochemical stains were performed at the discretion of the pathologists. Characteristics of histologic transformation in BM were analyzed.

RESULTS

3 of 24 patients (12.5%) with both resected BM and primary non-small-cell lung cancers (NSCLCs) had evidence of histologic transformation in BM. One case with SCC transformed to adenocarcinoma in brain, one case with adenocarcinoma transformed to SCLC, and another case with adenocarcinoma transformed to SCC. The three cases of histologic transformation were all spontaneous and had not tested gene status.

CONCLUSIONS

We disclosed the histologic transformation of NSCLC in BM at a frequency not as low as expected, and speculated it as an evolution promoted by intratumor heterogeneity, though it warrants further prospective multi-institution investigations with comprehensive molecular analysis. Our findings provided further impetus for surgery when the metastatic or recurrent lesion is resectable, and repeated pathologic evaluation to help tailor individualized treatment.

Genetic alterations and protein expression in combined small cell lung cancers and small cell lung cancers arising from lung adenocarcinomas after therapy with tyrosine kinase inhibitors

There are 2 hypotheses regarding the mechanism underlying the adenocarcinoma (AD) to small cell lung cancer (SCLC) transition in patients receiving Tyrosine kinase inhibitor (TKI) therapy: 1) AD gives rise to SCLC owing to the pressure of the TKI therapy, and 2) the SCLC coexists with the AD de novo, but is not detected in biopsy specimens of the heterogeneous tumor. In this study, we try to address this issue by examination the genetic alteration and protein expression profile between SCLC arising from AD, and SCLC in combined small cell lung cancers (CSCLC). In the former, the SCLC had the same genetic profile as the AD, and we strongly suggest that the transition was a consequence of TKI therapy. In the latter, genetic alterations and protein expression tended to differ between the NSCLC and SCLC components of the CSCLC. The results showed that EGFR and KRAS mutation were found in 1 but not both component of CSCLC, and the NSCLC component usually expressed the EGFR and RB1 proteins, whereas the SCLC component did not. This finding indicates that the NSCLC and SCLC components arose separately and that CSCLC are unsuitable for TKI therapy despite the presence of sensitive EGFR mutations.

[Advances in the Transformation to Small Cell Lung Cancer from Non-small Cell Lung Cancer Following Acquired Drug-resistance to EGFR Tyrosine Kinase Inhibitors]

表皮生长因子受体酪氨酸激酶抑制剂（epidermal growth factor receptor tyrosine kinase inhibitors, EGFR TKIs）在治疗携带EGFR基因敏感突变的非小细胞肺癌（non-small cell lung cancer, NSCLC）中已取得显著疗效，但是，耐药的产生几乎是不可避免的，常见的耐药机制包括T790M突变、cMET基因扩增等。目前已有文献报道EGFR-TKI耐药的机制之一为NSCLC转化为小细胞肺癌（small cell lung cancer, SCLC），大约占3%-15%，是一种重要的少见耐药机制，并不为人们所深入了解。本文从“共同起源”和“转化时间节点”两个角度对其进行了归纳总结，重点探讨了其转化的可能机制，目前提出的两种可能转化机制分别为肿瘤异质性假说、NSCLC转化为SCLC假说，还涉及了许多分子水平的改变，如RB1基因缺失、P53基因失活、PTEN M264I基因突变等，同时对该种转化的发病特点、治疗策略等方面进行了归纳与总结。目前仍有许多问题需要进一步研究和解决。

A TERT-CLPTM1 locus polymorphism (rs401681) is associated with EGFR mutation in non-small cell lung cancer

Telomere length is associated with lung carcinogenesis, and recent studies have focused on telomere-maintaining genes and their polymorphisms. Cancer susceptibility of the rs401681 polymorphism, located in the TERT-CLPTM1L locus, has been studied in many cancers. We examined the clinicopathological and prognostic value of rs401681 variants in lung cancer. The relationship between rs401681 variants and telomere length was analyzed in 134 non-small cell lung cancers (NSCLCs). The rs401681 polymorphism had the following genotype frequencies: C/C in 52.2% of the samples, C/T in 30.6%, and T/T in 17.2%. The T allele showed a strong correlation with EGFR mutation (p=0.037). Telomeres in the tumor samples were 3.26-fold longer, on average, than telomeres in matched normal samples (SD=0.48), and there were no differences in telomere length according to rs401681 polymorphism. Smoking was associated with telomere shortening (p=0.01). Survival analysis showed no prognostic value for rs401681 polymorphisms or telomere length in NSCLC. These results suggested that the rs401681 polymorphism contributes to lung carcinogenesis only in patients harboring an EGFR mutation. However, the polymorphism was not associated with survival; therefore, further comprehensive analysis should be performed.

Outcome of patients with lung adenocarcinoma with transformation to small-cell lung cancer following tyrosine kinase inhibitors treatment: A systematic review and pooled analysis

BACKGROUND

Lung adenocarcinoma can transform to small-cell lung cancer (SCLC) when resistance to tyrosine kinase inhibitors (TKIs) develops. This phenomenon has repeatedly been described in several case reports and small patient series. The characteristics and treatment outcomes of this population, however, have not been comprehensively reported.

METHODS

We performed a systematic review of the published literature to obtain explorative information on the clinical and pathological features and prognosis of the reported cases.

RESULTS

Twenty-five eligible publications were identified, contributing to 39 patients. The median time from initial diagnosis of lung adenocarcinoma to the transformation to SCLC (ttSCLC) was 19months (range 1-61months). The median survival after SCLC diagnosis was 6months. Female gender was significantly associated with longer ttSCLC at the multivariable analysis. Smoking status seemed to be associated with worse prognosis after the diagnosis of SCLC.

CONCLUSION

In this series of published cases, the transformation to a SCLC phenotype after an initial diagnosis of lung adenocarcinoma following TKI therapy appeared to be a late phenomenon. The prognosis after SCLC diagnosis is poor and current treatment strategies derived from primary SCLC seem to be largely inefficacious. New therapies are needed in the management of transformed SCLC.

Transformation to Small Cell Lung Cancer of Pulmonary Adenocarcinoma: Clinicopathologic Analysis of Six Cases

BACKGROUND

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are considered the first line treatment for a subset of EGFR-mutated non-small cell lung cancer (NSCLC) patients. Although transformation to small cell lung cancer (SCLC) is one of the known mechanisms of resistance to EGFR TKIs, it is not certain whether transformation to SCLC is exclusively found as a mechanism of TKI resistance in EGFR-mutant tumors.

METHODS

We identified six patients with primary lung adenocarcinoma that showed transformation to SCLC on second biopsy (n = 401) during a 6-year period. Clinicopathologic information was analyzed and EGFR mutation results were compared between initial and second biopsy samples.

RESULTS

Six patients showed transformation from adenocarcinoma to SCLC, of which four were pure SCLCs and two were combined adenocarcinoma and SCLCs. Clinically, four cases were EGFR-mutant tumors from non-smoking females who underwent TKI treatment, and the EGFR mutation was retained in the transformed SCLC tumors. The remaining two adenocarcinomas were EGFR wild-type, and one of these patients received EGFR TKI treatment.

CONCLUSIONS

NSCLC can acquire a neuroendocrine phenotype with or without EGFR TKI treatment.

Epidermal growth factor receptor (EGFR) mutations in small cell lung cancers: Two cases and a review of the literature

Activating mutations in the epidermal growth factor receptor (EGFR) gene are exceedingly rare in small cell lung cancer (SCLC). We present two cases of SCLC harboring EGFR mutations, one in an 82 year-old male smoker with a combined SCLC and adenocarcinoma with a novel D855H point mutation in exon 21, and the second in a 68 year-old female never smoker with the L858R point mutation in exon 21. The cases, accompanied by a review of the literature, highlight the importance of integration of clinicopathologic considerations and adherence to recently promulgated Guideline recommendations for molecular testing in lung cancer.

Small-Cell Lung Cancer Transformation in Patients With Pulmonary Adenocarcinoma: A Case Report and Review of Literature

Despite the demonstrated benefit from epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI) based therapies, EGFR mutant lung adenocarcinoma will eventually acquire drug resistance. Transformation to small-cell lung cancer (SCLC) is considered to be a rare resistance mechanism of EGFR-TKI therapy.We describe a case of a 46-year-old man presenting with refractory cough. Percutaneous transthoracic biopsy was performed and confirmed an EGFR exon 21 L858R lung adenocarcinoma. However, the patient relapsed after successful treatment with gefitinib for 1 year, at which point rebiopsy identified an SCLC and chemotherapy composed of platinum and pemetrexed was started. However, despite the brief success of chemotherapy, our patient died of aggressive cancer progression and complications of chemotherapy.Our case highlights the importance of rebiopsy when managing drug resistance and presents a possible origin of the transformed cells. We also summarize the clinical characteristics of cases involving transformed SCLC from previous studies and discuss whether it could be a new subtype of SCLC.

[Clinical Observation of Translating to Small Cell Lung Cancer Following Treatment with EGFR-Tyrosine Kinase Inhibitors in Lung Adenocarcinoma]

近年来, 非小细胞肺癌(non-small cell lung cancer, NSCLC)静脉化疗逐渐进入平台期, 缓解率(response rate, RR)、平均总生存期(overall survival, OS)无明显改善; 随着分子生物学发展, 以表皮生长因子受体(epidermal growth factor receptor, EGFR)为靶点的EGFR酪氨酸激酶抑制剂(EGFR-tyrosine kinase inhibitors, EGFR-TKIs)在NSCLC的治疗中疗效显著, 但患者最终均会出现耐药, 关于耐药机制目前尚未完全明确。本文详细报道1例49岁女性EGFR基因19外显子缺失突变肺腺癌患者, 在靶向治疗耐药后二次活检发现转化为小细胞肺癌(small cell lung cancer, SCLC), 予以SCLC化疗方案两周期有效; 通过分析患者诊疗过程、疗效, 对相关机制进展作一综述。

Transformation from non-small-cell lung cancer to small-cell lung cancer: molecular drivers and cells of origin

Lung cancer is the most common cause of cancer deaths worldwide. The two broad histological subtypes of lung cancer are small-cell lung cancer (SCLC), which is the cause of 15% of cases, and non-small-cell lung cancer (NSCLC), which accounts for 85% of cases and includes adenocarcinoma, squamous-cell carcinoma, and large-cell carcinoma. Although NSCLC and SCLC are commonly thought to be different diseases owing to their distinct biology and genomic abnormalities, the idea that these malignant disorders might share common cells of origin has been gaining support. This idea has been supported by the unexpected findings that a subset of NSCLCs with mutated EGFR return as SCLC when resistance to EGFR tyrosine kinase inhibitors develops. Additionally, other case reports have described the coexistence of NSCLC and SCLC, further challenging the commonly accepted view of their distinct lineages. Here, we summarise the published clinical observations and biology underlying tumours with combined SCLC and NSCLC histology and cancers that transform from adenocarcinoma to SCLC. We also discuss pre-clinical studies pointing to common potential cells of origin, and speculate how the distinct paths of differentiation are determined by the genomics of each disease.

Small-cell carcinoma in the setting of pulmonary adenocarcinoma: new insights in the era of molecular pathology

INTRODUCTION

Transformation into small-cell lung carcinoma (SCLC) has been reported as an evolution of lung adenocarcinoma acquiring resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI). However, spontaneous association of SCLC and adenocarcinoma also exists. We sought to compare patients' clinical features and mutation status of EGFR in each tumor component in these conditions.

METHODS

Our study is based on nine consecutive cases of SCLC, occurring synchronously or after a previous diagnosis of pulmonary adenocarcinoma, with or without TKI-based therapy, diagnosed in Marie Lannelongue Surgical Center, France, between 2001 and 2013. Molecular analysis by DNA direct sequencing was performed to detect EGFR mutations on formalin-fixated tissue mostly from surgically resected tumors.

RESULTS

Six patients had a metachronous occurrence of SCLC after adenocarcinoma (2 after TKI); three had a synchronous form. There were four combined SCLCs/adenocarcinomas. Seven adenocarcinoma components were EGFR mutated: five exon 19 deletions and two mutations in exon 21 (L833_V834delinsFL and L858R). Four SCLC components were EGFR mutated. Two cases occurred in never-smoker women with adenocarcinoma treated with TKI: one with E872 mutation in exon 21 and one combined SCLC/adenocarcinoma with exon 19 deletion in both components. Two cases were spontaneous: a SCLC with exon 19 deletion occurring after a nonmutated adenocarcinoma and a combined SCLC/adenocarcinoma with exon 21 mutation (L833_V834delinsFL) in both components.

CONCLUSION

SCLC developing in association with adenocarcinoma, either synchronously or metachronously, seem linked to EGFR mutation, regardless of TKI use. Our findings suggest that such associated cases should be tested for EGFR mutations.

Neuroendocrine tumours--challenges in the diagnosis and classification of pulmonary neuroendocrine tumours

Pulmonary neuroendocrine (NE) proliferations are a diverse group of disorders which share distinct cytological, architectural and biosynthetic features. Tumours composed of NE cells are dispersed among different tumour categories in the WHO classification of tumours and as such do not conform to a singular group with regards to treatment and prognosis. This is reflected by the highly variable behaviour of NE proliferations, ranging from asymptomatic, for instance in diffuse idiopathic pulmonary NE cell hyperplasia and tumourlets, to highly malignant cancers such as small cell lung cancer and large cell NE carcinoma. In this review NE proliferations are described as distinct entities ranging from low grade lesions to high grade cancers. The differential diagnoses are considered with each of the entries. Finally, mention is made of tumours which may show some NE features.

Rapid increase of serum neuron specific enolase level and tachyphylaxis of EGFR-tyrosine kinase inhibitor indicate small cell lung cancer transformation from EGFR positive lung adenocarcinoma?

We report the case of an 80-year-old male with relapsed EGFR exon 19 deletion lung adenocarcinoma treated with EGFR-tyrosine kinase inhibitor (TKI), but with poor response and rapid increase of serum neuron specific enolase (NSE). Repeat biopsy identified pathological transformation to small cell lung cancers (SCLC) retaining the same EGFR mutation. This case highlights routine serological testing of NSE may benefit for the lung adenocarcinoma patients resistant to TKIs.