Transformation to small-cell lung cancer as a mechanism of acquired resistance to crizotinib and alectinib

ALK inhibitors in cancer: mechanisms of resistance and therapeutic management strategies

Anaplastic lymphoma kinase (ALK) gene rearrangements have been identified as potent oncogenic drivers in several malignancies, including non-small cell lung cancer (NSCLC). The discovery of ALK inhibition using a tyrosine kinase inhibitor (TKI) has dramatically improved the outcomes of patients with ALK-mutated NSCLC. However, the emergence of intrinsic and acquired resistance inevitably occurs with ALK TKI use. This review describes the molecular mechanisms of ALK TKI resistance and discusses management strategies to overcome therapeutic resistance.

EML4-ALK fusions drive lung adeno-to-squamous transition through JAK-STAT activation

Human lung adenosquamous cell carcinoma (LUAS), containing both adenomatous and squamous pathologies, exhibits strong cancer plasticity. We find that ALK rearrangement is detectable in 5.1-7.5% of human LUAS, and transgenic expression of EML4-ALK drives lung adenocarcinoma (LUAD) formation initially and squamous transition at late stage. We identify club cells as the main cell-of-origin for squamous transition. Through recapitulating lineage transition in organoid system, we identify JAK-STAT signaling, activated by EML4-ALK phase separation, significantly promotes squamous transition. Integrative study with scRNA-seq and immunostaining identify a plastic cell subpopulation in ALK-rearranged human LUAD showing squamous biomarker expression. Moreover, those relapsed ALK-rearranged LUAD show notable upregulation of squamous biomarkers. Consistently, mouse squamous tumors or LUAD with squamous signature display certain resistance to ALK inhibitor, which can be overcome by combined JAK1/2 inhibitor treatment. This study uncovers strong plasticity of ALK-rearranged tumors in orchestrating phenotypic transition and drug resistance and proposes a potentially effective therapeutic strategy.

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.

Immune Resistance in Lung Adenocarcinoma

Lung cancer is the leading cancer killer worldwide, imposing grievous challenges for patients and clinicians. The incidence of lung adenocarcinoma (LUAD), the main histologic subtype of lung cancer, is still increasing in current-, ex-, and even non-smokers, whereas its five-year survival rate is approximately 15% as the vast majority of patients usually present with advanced disease at the time of diagnosis. The generation of novel drugs targeting key disease driver mutations has created optimism for the treatment of LUAD, but, as these mutations are not universal, this therapeutic line benefits only a subset of patients. More recently, the advent of targeted immunotherapies and their documented clinical efficacy in many different cancers, including LUAD, have started to change cancer management. Immunotherapies have been developed in order to overcome the cancer's ability to develop mechanisms of immune resistance, i.e., to adapt to and evade the host inflammatory and immune responses. Identifying a cancer's immune resistance mechanisms will likely advance the development of personalized immunotherapies. This review examines the key pathways of immune resistance at play in LUAD and explores therapeutic strategies which can unleash potent antitumor immune responses and significantly improve therapeutic efficacy, quality of life, and survival in LUAD.

Small cell transformation of ROS1 fusion-positive lung cancer resistant to ROS1 inhibition

Histologic transformation from non-small cell to small cell lung cancer has been reported as a resistance mechanism to targeted therapy in EGFR-mutant and ALK fusion-positive lung cancers. Whether small cell transformation occurs in other oncogene-driven lung cancers remains unknown. Here we analyzed the genomic landscape of two pre-mortem and 11 post-mortem metastatic tumors collected from an advanced, ROS1 fusion-positive lung cancer patient, who had received sequential ROS1 inhibitors. Evidence of small cell transformation was observed in all metastatic sites at autopsy, with inactivation of RB1 and TP53, and loss of ROS1 fusion expression. Whole-exome sequencing revealed minimal mutational and copy number heterogeneity, suggestive of "hard" clonal sweep. Patient-derived models generated from autopsy retained features consistent with small cell lung cancer and demonstrated resistance to ROS1 inhibitors. This case supports small cell transformation as a recurring resistance mechanism, and underscores the importance of elucidating its biology to expand therapeutic opportunities.

Prognostic value of TP53 concurrent mutations for EGFR- TKIs and ALK-TKIs based targeted therapy in advanced non-small cell lung cancer: a meta-analysis

Background

The prognostic significance of TP53 concurrent mutations in patients with epidermal growth factor receptor (EGFR)- or anaplastic lymphoma kinase (ALK)- mutated advanced non–small-cell lung cancer (NSCLC) who received EGFR-tyrosine kinase inhibitors (TKIs) or ALK-TKIs based targeted therapy remains controversial. Therefore, the present meta-analysis was performed to investigate the association between TP53 concurrent mutations and prognosis of patients with advanced NSCLC undergoing EGFR-TKIs or ALK-TKIs treatments.

Methods

Eligible studies were identified by searching the online databases PubMed, Embase, Medline, The Cochrane library and Web of Science. Hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated to clarify the correlation between TP53 mutation status and prognosis of patients. This meta-analysis was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement.

Results

In total, 15 studies with 1342 patients were included for final analysis. Overall, concurrent TP53 mutation was associated with unfavorable progression-free survival (PFS) (HR = 1.88, 95%CI: 1.59–2.23, p < 0.001, I² = 0.0%, P = 0.792) and overall survival (OS) (HR = 1.92, 95%CI: 1.55–2.38, p < 0.001, I² = 0.0%, P = 0.515). Subgroup analysis based on type of targeted therapy (EGFR-TKIs or ALK-TKIs, pathological type of cancer (adenocarcinoma only or all NSCLC subtypes) and line of treatment (first-line only or all lines) all showed that TP53 mutations was associated with shorter survivals of patients with EGFR-TKIs or ALK-TKIs treatments. Particularly, in patients with first-line EGFR-TKIs treatment, significantly poorer prognosis was observed in patients with TP53 concurrent mutations (pooled HR for PFS: 1.69, 95% CI 1.25–2.27, P < 0.001, I² = 0.0%, P = 0.473; pooled HR for OS: 1.94, 95% CI 1.36–2.76, P < 0.001, I² = 0.0%, P = 0.484). Begg’s funnel plots and Egger’s tests indicated no significant publication bias in this study.

Conclusions

This meta-analysis indicated that concurrent TP53 mutations was a negative prognostic factor and associated with poorer outcomes of patients with EGFR-TKIs or ALK-TKIs treatments in advanced NSCLC. In addition, our study provided evidence that TP53 mutations might be involved in primary resistance to EGFR-TKIs treatments in patients with sensitive EGFR mutations in advanced NSCLC.

Third-Generation TKI Resistance Due to SCLC Transformation: A Case Report and Brief Review

Objective

We reported a case of pathologic type transformed from adenocarcinoma to small-cell lung cancer (SCLC) after being treated with third-generation epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI).

Materials and methods

The lung cancer pathologic type was transformed from adenocarcinoma to SCLC after the treatment of third-generation EGFR-TKI for 4.3 months. Four times of lung biopsies were conducted at a different time and different lesions. And the patient was treated with a variety of regimens after SCLC transformation, including etoposide combined with carboplatin (EC), irinotecan combined with oxaliplatin (IO), Abraxane, and Apatinib. These treatments got a good response, but quick progression. We also monitored the dynamic change of serum neuron-specific enolase (NSE) and pro-gastrin releasing peptide (Pro-GRP).

Results

Adenocarcinoma could transform into SCLC after the treatment of TKI. Tumor cells were heterogeneity, so adenocarcinoma and SCLC could be co-existed. The fluctuation of the NSE was consistent with the response of treatment and the progression of the tumor.

Conclusion

Regimens for the primary SCLC were also available for the transformed SCLC, but the duration of the response was short. NSE could be an effective biomarker for dynamic monitoring of the efficacy in SCLC transformation.

Therapeutic decision based on molecular detection of resistance mechanism in an ALK-rearranged lung cancer patient: a case report

Background

The use of tyrosine kinase inhibitors (TKIs) of ALK is the therapy of choice for ALK-fusion patients. Unfortunately, all patients under this kind of treatment eventually develop acquired resistance through several well-known mechanisms, such as acquisition of a secondary mutation within the kinase domain, activation of a bypass signaling pathway, or a histological change like small-cell lung cancer transformation. At the time of progression, a tissue re-biopsy may give important molecular and morphological information regarding the mechanisms driving resistance to ALK TKIs. However, this procedure is not always feasible and it may not reflect the tumor heterogeneity, and therefore gives incomplete information. To overcome these drawbacks, the analysis of circulating tumor DNA (ctDNA) isolated from plasma, the so-called liquid biopsy, is emerging as a noninvasive and useful tool for detecting resistance mutations. Secondary resistance mutations are common in second-generation TKIs resistant patients and among these, Gly1202Arg (p.G1202R) emerged as the most frequent mutation.

Case presentation

We have treated an ALK-positive lung adenocarcinoma patient with a sequential strategy of ALK TKIs. Patient follow-up was performed combining clinical, radiological, and molecular profiling. ctDNA was isolated from plasma and by means of ultra-deep next generation sequencing; we searched for secondary ALK resistance mutations on exons 21-25. ALK mutation Gly1202Arg (G1202R) was detected. We have documented consistency between plasma levels of G1202R mutation and radiological progression or improvement.

Conclusion

Liquid biopsy appears to be a promising tool to anticipate progression and to drive the therapeutic strategy based upon ALK resistance mutations.

[Current Status for Anaplastic Lymphoma Kinase in Non-small Cell Lung Cancer]

The incidence of ALK gene rearrangement in non-small cell lung cancer (NSCLC) was about 3% to 5%. ALK gene inhibitors have made great breakthrough in recent years, significantly extending the survival period of patients with ALK(+) advanced NSCLC. But the majority of patients will be acquired drug resistance after treatment. This article has been explained separately from the ALK genetic background, the detection method, the treatment of the three generations of ALK inhibitors and the strategy after drug resistance. It is desire to have reference value and reference meaning for clinical work.
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Non-small cell to small cell lung cancer on PD-1 inhibitors: two cases on potential histologic transformation

Introduction

Histologic transformation from non-small cell lung cancer (NSCLC) to small cell lung cancer (SCLC) is a well-recognized mechanism of resistance in EGFR-mutant adenocarcinoma upon treatment with TKIs, but rarely reported with programmed death1 (PD-1) inhibitors. We report two cases of potential transformation during treatment with PD-1 inhibitors.

Case presentations

Case 1, a 65-year-old man was diagnosed with stage IVa lung adenocarcinoma on pleural fluid cytology. He received six cycles of carboplatin and pemetrexed, then maintained on pemetrexed. He had disease progression after nine cycles of pemetrexed and was switched to nivolumab. He progressed after five cycles of nivolumab. Core biopsy of the lung mass revealed SCLC. Case 2, a 68-year-old man was diagnosed with two primary NSCLCs and underwent resection. He had recurrence after several months and was treated with four cycles of carboplatin, paclitaxel, and pembrolizumab on clinical trial, with partial response. He was continued on pembrolizumab and had disease progression after 30 cycles. Biopsy of the new lesions showed SCLC.

Discussion

Histologic transformation from NSCLC to SCLC can be explained by the presence of a common cell precursor. Proposed molecular mechanisms include loss of RB1, TP53 mutations, and MYC amplification. The distinction between transformation and mixed histology tumors is challenging, especially when pathologic material used for the initial diagnosis is limited. The possibility of a second metachronous primary lung cancer cannot be excluded in our cases.

Conclusion

Histologic transformation with PD-1 inhibitors could be under-recognized. Disease progression should prompt re-biopsy to uncover new histology and change in treatment. Future studies are needed to elucidate mechanisms and predictors of transformation.

Personalized therapy for lung cancer: striking a moving target

Molecular targeted therapy heralded a new era for the treatment of patients with oncogene-driven advanced-stage non-small-cell lung cancer (NSCLC). Molecular testing at the time of diagnosis guides therapy selection, and targeted therapies in patients with activating mutations in EGFR, BRAF, and rearrangements in anaplastic lymphoma kinase (ALK) and ROS1 have become part of routine care. These therapies have extended the median survival from a mere few months to greater than 3 years for patients with stage 4 disease. However, despite the initial success, these treatments are eventually met with molecular resistance. Selective pressure leads to cellular adaption to maintain cancer growth, making resistance complex and the treatment challenging. This review focuses on recent advances in targeted therapy, mechanisms of resistance, and therapeutic strategies to overcome resistance in patients with lung cancer.

Sequential ALK Inhibitors Can Select for Lorlatinib-Resistant Compound ALK Mutations in ALK-Positive Lung Cancer

The cornerstone of treatment for advanced ALK-positive lung cancer is sequential therapy with increasingly potent and selective ALK inhibitors. The third-generation ALK inhibitor lorlatinib has demonstrated clinical activity in patients who failed previous ALK inhibitors. To define the spectrum of ALK mutations that confer lorlatinib resistance, we performed accelerated mutagenesis screening of Ba/F3 cells expressing EML4-ALK. Under comparable conditions, N-ethyl-N-nitrosourea (ENU) mutagenesis generated numerous crizotinib-resistant but no lorlatinib-resistant clones harboring single ALK mutations. In similar screens with EML4-ALK containing single ALK resistance mutations, numerous lorlatinib-resistant clones emerged harboring compound ALK mutations. To determine the clinical relevance of these mutations, we analyzed repeat biopsies from lorlatinib-resistant patients. Seven of 20 samples (35%) harbored compound ALK mutations, including two identified in the ENU screen. Whole-exome sequencing in three cases confirmed the stepwise accumulation of ALK mutations during sequential treatment. These results suggest that sequential ALK inhibitors can foster the emergence of compound ALK mutations, identification of which is critical to informing drug design and developing effective therapeutic strategies.Significance: Treatment with sequential first-, second-, and third-generation ALK inhibitors can select for compound ALK mutations that confer high-level resistance to ALK-targeted therapies. A more efficacious long-term strategy may be up-front treatment with a third-generation ALK inhibitor to prevent the emergence of on-target resistance. Cancer Discov; 8(6); 714-29. ©2018 AACR.This article is highlighted in the In This Issue feature, p. 663.

Precision medicine against ALK-positive non-small cell lung cancer: beyond crizotinib

Anaplastic lymphoma kinase (ALK) rearrangements represent the molecular driver of a subset of non-small cell lung cancers (NSCLCs). Despite the initial response, virtually all ALK-positive patients develop an acquired resistance to the ALK inhibitor crizotinib, usually within 12 months. Several next-generation ALK inhibitors have been developed in order to overcome crizotinib limitation, providing an unprecedented survival for this subset of patients. The aim of this review to summarize the current knowledge on ALK tyrosine kinase inhibitors (TKIs) in the treatment of advanced ALK-positive NSCLC, focusing on the role of novel ALK inhibitors in this setting. In addition, we will discuss their role in the pharmacological management of ALK-positive brain metastasis. Next-generation ALK inhibitors showed an impressive clinical activity in ALK-positive NSCLC, also against the sanctuary site of CNS. Sequential therapy with ALK TKIs appears to be effective in patients who fail a first ALK TKI and translates in clinically meaningful benefit. However, these agents display different activity profiles against crizotinib resistance mutation; therefore re-genotyping the disease at progression in order to administer the right TKI to the right patient is going to be necessary to correctly tailor the treatment. To avoid repeated invasive procedure, noninvasive methods to detect and monitor ALK rearrangement are under clinical investigation.

Anaplastic lymphoma kinase (ALK)-expressing Lung Adenocarcinoma with Combined Neuroendocrine Component or Neuroendocrine Transformation: Implications for Neuroendocrine Transformation and Response to ALK-tyrosine Kinase Inhibitors

BACKGROUND

Anaplastic lymphoma kinase tyrosine kinase inhibitors (ALK-TKIs) are usually effective in lung adenocarcinoma patients with anaplastic lymphoma kinase (ALK) rearrangement. However, even after a good response to ALK-TKI therapy, most patients acquire resistance to these agents. Histological transformation is one of several suggested mechanisms of acquired resistance to ALK-TKIs. The clinicopathologic features of four patients with ALK-expressing adenocarcinoma and neuroendocrine features were analyzed.

METHODS

We selected combined neuroendocrine differentiation in pulmonary adenocarcinoma cases with positive ALK immunostaining. Neuroendocrine differentiation was confirmed by CD56 immunohistochemical stain. Additional ALK fluorescence in situ hybridization (FISH) study and epidermal growth factor receptor (EGFR) mutation tests were also performed.

RESULTS

All four cases were positive for ALK immunohistochemistry and no EGFR mutations were detected. Interestingly, the results of ALK FISH assays showed rearrangement in only two cases. Three cases showed combined adenocarcinoma and neuroendocrine component without history of ALK-TKI administration; one of them was treated with crizotinib and experienced partial tumor regression. The remaining case had an adenocarcinoma at initial biopsy and she showed a partial response to crizotinib, and neuroendocrine changes were visible on second biopsy. Then she was treated with ceritinib and achieved a partial response.

CONCLUSION

We suggest that ALK-rearranged adenocarcinoma with combined neuroendocrine component is responsive to ALK-TKIs. Moreover, even after neuroendocrine transformation as a result of resistance to ALK-TKIs, the tumor may have partial response to second generation ALK-TKIs.

Small cell lung cancer transformation from EGFR-mutated lung adenocarcinoma: A case report and literatures review

Epithelial growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) have markedly improved the response of non-small cell lung cancer (NSCLC) with EGFR-mutant patients. However, these patients inevitably come cross acquired resistance to EGFR-TKIs. The transformation of lung adenocarcinoma to small cell lung cancer (SCLC) following treatment with EGFR-TKIs is rare, which leads to resistance to EGFR-TKIs. The present case concerns a case of a 38-year-old man presenting with cough and dyspnea. Radical resection was performed and confirmed an EGFR exon 21 L858R lung adenocarcinoma. However, the patient suffered pleural metastasis after successful treatment with surgery and adjuvant treatment. So, erlotinib was administered with 18 months. Because of enlarged pleural nodule, repeat biopsy identified an SCLC and chemotherapy was started. However, despite the brief success of chemotherapy, our patient suffered brain metastasis. Our case emaphsizes both the profile of transformation from NSCLC to SCLC and the importance of repeat biopsy dealing with drug resistance. We also summarize the clinical characteristics, mechanisms, predictors of SCLC transformation, treatment after transformation and other types of transformation to SCLC.

Tumor Resistance against ALK Targeted Therapy-Where It Comes From and Where It Goes

Anaplastic lymphoma kinase (ALK) is a validated molecular target in several ALK-rearranged malignancies, particularly in non-small-cell lung cancer (NSCLC), which has generated considerable interest and effort in developing ALK tyrosine kinase inhibitors (TKI). Crizotinib was the first ALK inhibitor to receive FDA approval for ALK-positive NSCLC patients treatment. However, the clinical benefit observed in targeting ALK in NSCLC is almost universally limited by the emergence of drug resistance with a median of occurrence of approximately 10 months after the initiation of therapy. Thus, to overcome crizotinib resistance, second/third-generation ALK inhibitors have been developed and received, or are close to receiving, FDA approval. However, even when treated with these new inhibitors tumors became resistant, both in vitro and in clinical settings. The elucidation of the diverse mechanisms through which resistance to ALK TKI emerges, has informed the design of novel therapeutic strategies to improve patients disease outcome. This review summarizes the currently available knowledge regarding ALK physiologic function/structure and neoplastic transforming role, as well as an update on ALK inhibitors and resistance mechanisms along with possible therapeutic strategies that may overcome the development of resistance.

Resisting Resistance: Targeted Therapies in Lung Cancer

Drug resistance inevitably limits the efficacy of all targeted therapies including tyrosine kinase inhibitors (TKIs). Understanding the biological underpinnings of TKI resistance is key to the successful development of future therapeutic strategies. Traditionally, mechanisms of TKI resistance have been viewed under a dichotomous lens. Tumor cells are TKI-sensitive or TKI-refractory, exhibit intrinsic or acquired resistance, and accumulate alterations within or outside the target to promote their survival. Such classifications facilitate our comprehension of an otherwise complex biology, but are likely an oversimplification. Recent studies underscore the multifaceted, genetically heterogeneous nature of TKI resistance, which evolves dynamically with changes in therapy. In this Review, we provide a broad framework for understanding the diverse mechanisms of resistance at play in oncogene-driven lung cancers.

Possible adverse effects of immunotherapy in non-small cell lung cancer; treatment and follow-up of three cases

In the past decade novel agents are on the market for non-small cell lung cancer adenocarcinoma based on pharmacogenomics. The epidermal growth factor receptor mutation, anaplastic lymphoma kinase and programmed death-ligand 1 investigation is necessary in the everyday clinical practice for the oncologic patient. Immunotherapy is nowadays the novel therapy for advanced stage non-small cell lung cancer with two agents nivolumab and pembrolizumab. In the current case series we will present adverse effects from our centers and comment on the treatment and follow-up of the patients.

Patients harboring ALK rearrangement adenocarcinoma after acquired resistance to crizotinib and transformation to small-cell lung cancer: a case report

Anaplastic lymphoma kinase (ALK) rearrangement responds to ALK tyrosine kinase inhibitors (TKIs) in lung cancer. Many cases ultimately acquire resistance to crizotinib. Resistance, including ALK-dominant or ALK non-dominant, mechanisms have been described. Transformation to small-cell lung cancer is rare. Herein, we report a 49-year-old man diagnosed with adenocarcinoma, who was negative for EGFR and ALK genes as detected by reverse transcription polymerase chain reaction, and was treated with crizotinib. A new biopsy showed a small-cell lung cancer after disease progression. Then, next-generation sequencing (NGS) was carried out and detected a TP53 gene mutation, an ALK rearrangement, and no loss of the retinoblastoma gene (RB). Although a regimen for small-cell lung cancer may be one treatment option, a heterogeneous tumor may exist at the time of diagnosis and manifest during the course of disease.

Targeting ALK: Precision Medicine Takes on Drug Resistance

Anaplastic lymphoma kinase (ALK) is a validated molecular target in several ALK-rearranged malignancies, including non-small cell lung cancer. However, the clinical benefit of targeting ALK using tyrosine kinase inhibitors (TKI) is almost universally limited by the emergence of drug resistance. Diverse mechanisms of resistance to ALK TKIs have now been discovered, and these basic mechanisms are informing the development of novel therapeutic strategies to overcome resistance in the clinic. In this review, we summarize the current successes and challenges of targeting ALK.

SIGNIFICANCE

Effective long-term treatment of ALK-rearranged cancers requires a mechanistic understanding of resistance to ALK TKIs so that rational therapies can be selected to combat resistance. This review underscores the importance of serial biopsies in capturing the dynamic therapeutic vulnerabilities within a patient's tumor and offers a perspective into the complexity of on-target and off-target ALK TKI resistance mechanisms. Therapeutic strategies that can successfully overcome, and potentially prevent, these resistance mechanisms will have the greatest impact on patient outcome. Cancer Discov; 7(2); 137-55. ©2017 AACR.

Molecular Mechanisms of Resistance to First- and Second-Generation ALK Inhibitors in ALK-Rearranged Lung Cancer

Advanced, anaplastic lymphoma kinase (ALK)-positive lung cancer is currently treated with the first-generation ALK inhibitor crizotinib followed by more potent, second-generation ALK inhibitors (e.g., ceritinib and alectinib) upon progression. Second-generation inhibitors are generally effective even in the absence of crizotinib-resistant ALK mutations, likely reflecting incomplete inhibition of ALK by crizotinib in many cases. Herein, we analyzed 103 repeat biopsies from ALK-positive patients progressing on various ALK inhibitors. We find that each ALK inhibitor is associated with a distinct spectrum of ALK resistance mutations and that the frequency of one mutation, ALK^G1202R, increases significantly after treatment with second-generation agents. To investigate strategies to overcome resistance to second-generation ALK inhibitors, we examine the activity of the third-generation ALK inhibitor lorlatinib in a series of ceritinib-resistant, patient-derived cell lines, and observe that the presence of ALK resistance mutations is highly predictive for sensitivity to lorlatinib, whereas those cell lines without ALK mutations are resistant.

SIGNIFICANCE

Secondary ALK mutations are a common resistance mechanism to second-generation ALK inhibitors and predict for sensitivity to the third-generation ALK inhibitor lorlatinib. These findings highlight the importance of repeat biopsies and genotyping following disease progression on targeted therapies, particularly second-generation ALK inhibitors. Cancer Discov; 6(10); 1118-33. ©2016 AACRSee related commentary by Qiao and Lovly, p. 1084This article is highlighted in the In This Issue feature, p. 1069.

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.