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

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.

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.

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.