Sustained Clinical Response to 4th-Line Therapy with Selpercatinib in RET Fusion-Positive Combined Small Cell Lung Cancer

Abstract

Objective

Combined small cell lung cancer (C-SCLC) is a relatively rare subtype of small cell lung cancer (SCLC) which combines SCLC and any component of non-small cell carcinoma (NSCLC). Patients diagnosed with C-SCLC are currently recommended to receive the same treatment as SCLC cases in the absence of clear evidence suggesting different strategies. The genomic profiling of C-SCLC is rarely studied. Herein, we report a case of extensive-stage C-SCLC harboring the KIF5B-RET fusion before first-line therapy and with persistent sensitivity to fourth-line selpercatinib treatment is reported.

Materials and Methods

Molecular and pathological features were evaluated using transbronchial lung biopsy, immunohistochemical (IHC) staining and next-generation sequencing (NGS).

Results

NGS revealed the KIF5B-RET fusion in the C-SCLC tumor. The patient had a progression-free survival (PFS) surpassing 14 months after selpercatinib treatment, with ongoing clinical response in 4th-line treatment.

Conclusion

This case highlights the importance of comprehensive molecular testing in C-SCLC for selecting the optimal treatment. Although RET fusion is rare in patients with C-SCLC, its identification and treatment with selective RET inhibitors may contribute to clinical benefits.

Keywords:

• combined small cell lung cancer
• rearranged during transfection
• selpercatinib
• next-generation sequencing

Data Sharing Statement

All inquiries can be directed to the corresponding authors.

Ethics Statement and Consent for Publication

Institutional approval was not required to publish the case details. The patient provided written informed consent to the publication of this case report and any accompanying images.

Acknowledgment

The authors thank the patient and her family for their support of this study.

Disclosure

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

This work was supported by Sichuan University Innovation Research Project, Grant/Award Number: 2022SCUH0018, Sichuan University.