# Next generation sequencing guided treatment of ALK tyrosine kinase inhibitor induced long survival in lung squamous cell carcinoma harboring ROS1 gene fusions: a case report and literature review

## TL;DR

A rare case of lung squamous cell carcinoma with a ROS1 gene fusion achieved long-term survival using targeted therapies guided by next-generation sequencing.

## Contribution

Demonstrates the effectiveness of sequential ALK and ROS1 tyrosine kinase inhibitors in a rare LUSC case with genomic and immune monitoring.

## Key findings

- The patient achieved 42 months of survival with sequential ALK-TKI and ROS1-TKI treatment.
- NGS revealed changing genomic patterns during treatment, supporting precision medicine approaches.
- Treatment increased CD8+ T-cell infiltration and PD-L1 expression in the tumor microenvironment.

## Abstract

Approximately 1–2% of non-small cell lung cancer (NSCLC) cases harbor ROS1 gene fusions. However, lung squamous cell carcinoma (LUSC) patients with ROS1 rearrangements remain exceptionally rare. Current targeted therapies for LUSC harboring ALK, ROS1, or EGFR mutations are typically guided by protocols established for lung adenocarcinoma. Here, we present a case of advanced LUSC with ROS1 fusion who achieved prolonged survival (42 months) through sequential treatment with ALK tyrosine kinase inhibitor (ALK-TKI) and ROS1-TKI. Notably, this patient’s therapeutic management was critically informed by serial next-generation sequencing (NGS), demonstrating the value of precision medicine. Genomewide copy number profiles for the three clinical specimens demonstrate distinct genomic alteration patterns implying tumor genome signature changes over treatment and disease development. Laboratory immunofluorescence analysis of tumor biopsies further revealed treatment-induced modulation of tumor immune microenvironment (TIME), characterized by increased CD8 + T-cell infiltration and increased PD-L1 expression on tumor cells over treatment. Peripheral monocyte profiling of the patient post-Repotrectinib and localized radiotherapy showed 75% CD8+/CD3 + T cells, 14.2% CD4+/CD3 + T cells, 3.95% regulatory T cells (Tregs), and 38% PD-1 + CD3 + T cells. These systemic T cell dynamics mirror the immunophenotype observed in the tumor microenvironment. Furthermore, we also provide a comprehensive review of recent clinical advancements in ALK/ROS1-TKI for NSCLC, including mechanistic insights into TKI resistance development. This case underscores the therapeutic potential of molecular-targeted agents in LUSC and highlights the essential role of NGS-guided precision oncology.