An EGFR-mutated Lung Adenocarcinoma Undergoing Squamous Cell Carcinoma Transformation Exhibited a Durable Response to Afatinib

Transformation of adenocarcinoma to squamous cell carcinoma as a source of EGFR-TKI resistance: A case report and literature review

In general, non-small cell lung cancer patients with epidermal growth factor receptor (EGFR) mutations respond to tyrosine kinase inhibitors (TKIs). However, most patients experience resistance within 1-2 years after treatment. The histological explanation for the acquired resistance is that malignant transformation occurs during cancer treatment. To date, the transformation from adenocarcinoma to squamous cell carcinoma associated with EGFR-TKI use remains poorly reported. We report a case of stage IV lung adenocarcinoma with EGFR mutations that converted to squamous cell carcinoma due to long-term administration of EGFR-TKIs. This report strengthens histological evolution as a source of acquired drug resistance.

T790M mutation positive squamous cell carcinoma transformation from EGFR-mutated lung adenocarcinoma after low dose erlotinib: A case report and literature review

RATIONALE

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are widely used for the treatment of EGFR mutation positive advanced nonsmall cell lung cancer (NSCLC); however, acquired resistance is known to develop during these treatments. Among these mechanisms, histological transformation is seldom encountered. Although platinum based chemotherapy has been reported to be effective in the treatment of patients with small cell lung cancer transformation, there is a lack of information on the treatment of patients with squamous cell carcinoma (SQ) transformation.

PATIENT CONCERNS AND DIAGNOSIS

An 80-year-old nonsmoking woman was referred to our hospital because of an abnormal shadow on her chest radiograph. Diagnostic bronchoscopy was performed and pathological examination revealed adenocarcinoma. Mutation analysis of the EGFR gene revealed deletion of E746-A750 in exon 19. She refused both surgical treatment and radiation therapy, and preferred periodic radiologic follow-up. Unfortunately, approximately a year and a half after the initial diagnosis, the primary lesion enlarged, and many pleural nodules were newly detected (clinically T4N2M1a, stage IVA).

INTERVENTIONS AND OUTCOMES

Based on EGFR mutation analysis, a reduced dose of daily erlotinib was prescribed, which achieved a partial response and 34 months of progression-free survival (PFS). A repeated biopsy with an endobronchial cryoprobe was performed on the enlarged primary lesion. Pathological examination revealed SQ harboring an identical EGFR mutation with a secondary EGFR T790M mutation. Osimertinib 80 mg once a day was started as second line therapy, which resulted in 8 months of PFS and 15 months of survival.

LESSON

The literature review and our report suggest that osimertinib is a promising treatment for NSCLC regardless of histology if T790M is present as an acquired mutation.

Histologic Transformation in EGFR-Mutant Lung Adenocarcinomas: Mechanisms and Therapeutic Implications

With the advent of potent EGFR tyrosine kinase inhibitors (TKIs), the treatment landscape of EGFR-mutant lung adenocarcinomas has changed drastically in recent years. However, the development of resistance to EGFR TKIs remains a critical barrier to improving survival in these patients. Histologic transformations to small cell lung carcinoma, large cell neuroendocrine carcinoma, squamous cell carcinoma, and the sarcomatoid phenotype have been increasingly recognized as important mechanisms of resistance. In this article, we summarize the known biological bases for such phenotypic switches in regard to EGFR TKIs and describe novel pathways that might be harnessed to develop effective novel therapies for patients with EGFR-mutant non-small cell lung cancers.

Case Report: EGFR-Positive Early-Stage Lung Adenocarcinoma Transforming to Squamous Cell Carcinoma After TKI Treatment

The histological transformation from epidermal growth factor receptor (EGFR)-mutated adenocarcinoma (ADC) to squamous cell carcinoma (SCC) after tyrosine kinase inhibitor (TKI) treatment is rare. We present a case of a patient who transitioned from early-stage primary lung ADC with partial squamous differentiation, EGFR mutation and amplification, to adrenal gland metastasis as SCC with EGFR amplification disappearance 115-months after surgery, during which gefitinib and local radiotherapy were utilized for the metastasis in the right femoral head and mediastinal lymph nodes. This case might indicate a possible mechanism of EGFR inhibition resistance with SCC transition and EGFR amplification loss from the initially well-responding ADC, especially those with SCC or partial squamous differentiation. The optimal post-progression therapy for ADC-SCC patients is challenging and further studies are needed.

Transformation from adenocarcinoma to squamous cell carcinoma associated with long-term administration of EGFR-TKIs

Although patients with non-small cell lung cancer exhibiting EGFR mutations generally respond to tyrosine kinase inhibitors (TKIs), the majority of patients acquire resistance ~1 year after treatment. EGFR T790M mutations, MET or HER2 amplifications and phenotypic transformations contribute to the mechanism of EGFR-TKI resistance. The transformation of small cell lung cancer frequently occurs, although few convert to squamous cell carcinoma associated with the administration of EGFR-TKIs. The current study reports a case of EGFR-mutated adenocarcinoma of the lung that transitioned to squamous cell carcinoma in association with long-term EGFR-TKIs administration.

Emerging Treatment Paradigms for EGFR-Mutant Lung Cancers Progressing on Osimertinib: A Review

Since its approval in April 2018, osimertinib has been widely adopted as first-line therapy for patients with advanced EGFR-mutant non -small cell lung cancer (NSCLC). Understanding osimertinib resistance mechanisms and currently available treatment options are essential to selecting optimal second line therapy for patients whose disease progresses during front-line osimertinib. Using data compiled from 6 osimertinib-resistance series, we describe here the heterogeneous profile of EGFR-dependent and independent mechanisms of osimertinib treatment failure. We identified MET alterations (7%-24%), EGFR C797X (0%-29%), SCLC transformation (2%-15%), and oncogene fusions (1%-10%) as the most common mechanisms of resistance. This review provides an evidence-based, algorithmic approach to the evaluation and management of post-osimertinib progression as well as a compendium of active, enrolling clinical trials for this population.

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.