Prognostic Value of EGFR Mutation Subtypes After Linac-Based Stereotactic Radiosurgery or Fractionated Stereotactic Radiotherapy for Brain Metastasis From EGFR-Mutated Non-Small Cell Lung Cancer.

BACKGROUND

This study aimed to evaluate the differences in common types of epidermal growth factor receptor (EGFR) mutations in non-small cell lung cancer (NSCLC) with brain metastasis (BM) treated using linear accelerator-based stereotactic radiosurgery (SRS) and fractionated stereotactic radiotherapy (fSRT).

METHODS

Between January 2011-December 2023, among 294 consecutive patients with BM from NSCLC, 84 patients with EGFR-mutated NSCLC were enrolled in this study.

RESULTS

The median follow-up time after SRS/fSRT was 20.1 months (range: 0.6-109.7 months), while the median overall survival (mOS) after SRS/fSRT was 25.1 months (95% confidence interval [CI]: 18.4-33.5 months). The mOS after initial treatment for NSCLC was 56.2 months (95% CI: 41.7-77.0 months). The mOS after SRS/fSRT in 34 patients with exon 19 deletions and 45 patients with exon 21 mutations with L858R was 20.4 months (95% CI: 13.6-55.9 months) and 28.5 months (95% CI: 16.2-33.5). The two groups showed no difference in the mOS. In univariate analyses using the Cox proportional hazards model, no prognostic factors associated with prolonged survival were identified except for good pretreatment Karnofsky Performance Status score and no prior tyrosine kinase inhibitor use before SRS/fSRT in EGFR-mutated NSCLC. There was no difference in both distant failure and local control in the two groups.

CONCLUSION

The difference in survival between EGFR subtypes (exon 21 L858R mutations vs. exon 19 deletion) was not observed after SRS/fSRT in NSCLC.