Exploration of radiotherapy strategy for brain metastasis patients with driver gene positivity in lung cancer

Objective: To assess the disparities in effectiveness and identify outcome predictors in the treatment of a targeted -first and radiotherapy -first regimen with driver gene -positive lung cancer brain metastases. Materials and Methods: This retrospective study analyzed patients with driver gene -positive lung cancer brain metastases who received first -targeted and first -radiotherapy regimens, respectively, with SIB-WBRT (whole brain tissue 40 Gy/20 fractions, tumor tissue boosted to 56-60 Gy/20 fractions) and local irradiation (prescription dose range of 20-60 Gy/2-25 fractions, most commonly delivered as 30 Gy/5 fractions, with a BED range of 28-100.8 Gy) at Peking Union Medical College Hospital from September 2015 to December 2021. The primary endpoint was intracranial progression free survival (iPFS). Secondary endpoints included overall survival (OS), intracranial new lesions, and tumor control. The Kaplan -Meier method was utilized to depict and estimate iPFS, OS, intracranial new lesions and tumor control. The Cox regression analysis was conducted to assess the association between relevant factors and outcomes. Results: 88 patients were enrolled in targeted -first and radiotherapy -first regimen, totally. And no difference was found in the comparison of iPFS between the two groups (HR=1.180, 95%CI: 0.622-2.237, P=0.613). No difference was found in the comparison of OS between the two groups (HR=1.208, 95%CI: 0.679-2.150, P=0.520). No difference was found in the comparison of intracranial new lesions between the two groups (HR=1.184, 95%CI: 0.569-2.463, P=0.652). There was a difference in the local control time between the two groups, with radiotherapy -first regimen being superior (HR=2.397, 95% CI:1.453-3.954, P<0.001). Patient age (HR=1.054, 95%CI: 1.026- 1.082, P<0.001), radiotherapy modality (HR=0.128, 95%CI: 0.041-0.401, P<0.001), metastasis volume (HR=1.426, 95%CI: 1.209-1.682, P<0.001), number of metastases(HR=14.960, 95%CI: 1.990-112.444, P=0.009), extracranial disease status (HR=0.387, 95%CI: 0.170-0.880, P=0.023) and therapy sequence (HR=13.800, 95%CI: 4.455-42.751, P<0.001) were associated with local control. Conclusion: Targeted -first regimen was not found to improve patients' iPFS relative to radiotherapy -first regimen in patients with brain metastases. Radiotherapy -first regimen for brain metastases demonstrated superior local control compared to targeted -first regimen. Patient's age, radiotherapy modality, metastasis volume, number of metastases, extracranial disease status and therapy sequence may be related to local control of metastases.