Extensive-Stage Small Cell Carcinoma Transformation From EGFR Del19-Mutant Lung Adenocarcinoma on Gefitinib at the Twelfth-Year Follow-Up Case Report

Clinicopathologic features of histologic transformation in lung adenocarcinoma after treatment with epidermal growth factor receptor-tyrosine kinase inhibitors

BACKGROUND

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) may lead to drug resistance, and the underlying mechanism may involve histologic transformations to small cell carcinoma (SCC), squamous cell carcinoma (SqCC), and sarcomatoid carcinoma (SC). Although there are reports regarding these transformations, comprehensive analyses are limited.

METHODS

A total of 233 patients with primary lung adenocarcinoma treated with EGFR-TKIs were reviewed. Among them, 26 patients (11.1 %) showed histologic transformation.

RESULTS

Eleven patients (42.3 %) showed SCC and SqCC transformations respectively, and four patients (15.4 %) showed SC transformation. The median time from TKI initiation to transformation was 19.8 months (6.8-51.4) for SCC, 45.3 months (2.4-101.5) for SqCC, and 11.8 months (6.8-15.7) for SC. The median overall survival (OS) was 41.8 months (12.5-78.9), 72.6 months (18.8-112.7), and 23.7 months (17.4-34.4), respectively. The survival from transformation was 12.3 months (2.1-28.3), 16.9 months (0.7-43.2), and 11.4 months (1.6-23.5), respectively. The most common mutations were TP53, PTEN, and RB1 in SCC; TP53 and RB1 in SqCC; and TP53 and KMT2D in SC. SC transformation had the worst OS, followed by SCC and SqCC (p < 0.001). This prognosis difference was also reflected in the time to transformation after EGFR-TKI treatment (p = 0.005). However, survival after transformation was not associated with tumor subtypes (p = 0.536).

CONCLUSIONS

The analysis of mutation profiles and survival outcomes revealed that the transformation subtype affects prognosis. Additionally, the time taken to undergo transformation is critical for patient outcomes.