Prior Treatment for Non-small Cell Lung Cancer Is Associated With Improved Survival in Patients who Undergo Definitive Stereotactic Body Radiation Therapy for a Subsequent Lung Malignancy: A Retrospective Multivariate and Matched Pair Analysis.

BACKGROUND Despite occurring commonly, the prognoses of second early-stage non-small cell lung cancers (NSCLC) are not well known. METHODS The authors retrospectively reviewed the charts of inoperable patients who underwent thoracic stereotactic body radiation therapy (SBRT) from February 2007 to April 2019. Those with previous small cell lung cancers or SBRT treatments for tumors other than NSCLC were excluded. Multivariate Cox regression and a matched pair cohort analyses evaluated the prognoses of patients undergoing definitive SBRT for a new second primary. RESULTS Of 438 patients who underwent definitive SBRT for NSCLC, 84 had previously treated NSCLC. Univariate log-rank tests identified gender, Karnofksy performance status (KPS), prior lung cancer, anticoagulation use, and history of heart disease to correlate with overall survival (OS) (P<0.05). These factors were incorporated into a multivariate Cox regression model that demonstrated female sex (P=0.004, hazard ratio [HR]=0.68), KPS (P<0.001, HR=2.0), and prior lung cancer (P=0.049, HR=0.7) to be significantly associated with OS. A similar approach found only gender (P=0.017, HR=0.64) and tumor stage (P=0.02, HR=1.7) to correlate with relapse-free survival. To support the Cox regression analysis, propensity score matching was performed using gender, age, KPS, tumor stage, history of heart disease, and anticoagulation use. Kaplan-Meier survival analysis within the matched pairs found prior lung cancer to be associated with improved OS (P=0.011), but not relapse-free survival (P=0.44). CONCLUSIONS Compared with initial lung cancer SBRT inoperable cases, ablative radiotherapy for new primaries was associated with improved OS. Physicians should not be dissuaded from offering SBRT to such patients.