Local ablative radiotherapy on oligo-progression while continued on epidermal growth factor receptor tyrosine kinase inhibitors in advanced non-small cell lung cancer patients: A longer cohort

Background The effect of adding local ablative radiotherapy on oligo-progression while continuing EGFR-TKIs in advanced non-small cell Lung cancer (NSCLC) patients is to be determined. Methods Outcomes of patients with stage IV NSCLC harboring EGFR-activating mutations having <= 5 sites of oligo-progression while on EGFR-TKIs and given one to eight fractions of local ablative radiotherapy (LAR) were reviewed from 2012 to 2019. The time of starting first-line EGFR-TKIs to LAR is defined as progression-free survival 1 (PFS1; > one line of prior treatment allowed). The primary endpoint was PFS from LAR to further progression that led to stop of EGFR-TKIs (PFS2). The secondary endpoint was overall survival from LAR (OS). Factors affecting PFS2 and OS were analyzed with Cox regression. Results There were total 55 eligible patients. The median follow-up time was 13.3 months. Majority (89%) had sensitive mutations (exon 19 deletion and exon 21 L858R mutation). Total number of lesions treated were 75, including lung (n = 45), bone (n = 15), cervical lymph node (n = 1), adrenal (n = 1), and brain (n = 13). The median PFS2 was 6.9 months. The median OS was 25.1 months. On multivariable analysis, it was found that EGFR mutation type (exon 19 deletion / exon 21 L858R mutation vs. other rarer mutations), time from diagnosis to LAR within 70 days, and fewer lines of prior TKIs (1 or 2 vs. 3) had favorable effect on PFS2 (p = 0.006/0.00003; 0.046; 0.001/0.005, respectively). Conclusion LAR is a noninvasive and effective modality in treatment of oligo-progressive diseases for patients with EGFR mutations positive NSCLC while on EGFR-TKIs.