Efficacy of stereotactic body radiotherapy for oligoprogression on PD-1 axis inhibitors in advanced non-small cell lung cancer: A single-center retrospective study.

e21065 Background: Immunotherapy has brought considerable benefit for patients with advanced non-small cell lung cancer (NSCLC), while acquired resistance could occur, of which most were oligoprogression. Adding locoregional therapy into the current systematic treatment could significantly improve the survival of oligoprogressed group. One of the conventional locoregional therapy for oligoprogression is stereotactic body radiotherapy (SBRT), however efficacy of combing SBRT to the ongoing PD-1 axis inhibitors was unclear in oligoprogressive NSCLC. Methods: In this study, we retrospectively reviewed data of patients with advanced NSCLC, who received SBRT on oligoprogressive lesions after acquired resistance to PD-1 axis inhibitor (First line or more) in our hospital, between June 2015 and June 2019. Acquired resistance was defined as initial CR/PR (by RECIST) followed by progression/death. Oligo patterns of acquired resistance were defined as progression in ≤ 3 sites of disease. We summarized the locoregional control rate (LR), progression-free survival (PFS) and overall survival (OS) after SBRT. Results: A total of 18 patients were included, 5 females and 13 males. The median age was 63 years (range: 37-82). 10 (55.6%) patients had a PD-L1 expression > 1%, 13 (72.2%) received combination therapy (anti-PD-1+chemo/antivascular), duration of immunotherapy was longer than 24 months in 9 (50%) patients. After acquired resistance, 25 sites of oligoprogressive lesions were identified (11 in brain, 5 in lung, 3 in lymph node, 3 in bone, 2 in adrenal, 1 in liver), the median maximum dimension was 14.8 cm (range, 10 to 79 cm). The SBRT dose were 30-55 Gy/2-6 fx, with the median biological effective dose at 60 Gy (range: 45-124.8). At a median follow-up of 28.5 months (range: 15-60), 12 (48%) lesions achieved complete response, 7 (28%) had a partial response, 4 (16%) remains stable and 2 (8%) developed progressive disease. The 1 and 2 years’ LR were 100% and 77.8% respectively. The median PFS was 10 months (range: 7-18). Among them, 44.4% and 14.8% had a 1 and 2 years of PFS, and 87.5% and 60% achieved 1-year and 2-year survival respectively. Conclusions: We observed that SBRT for oligoprogression can improve disease control and bring survival benefit, suggesting that SBRT could be considered in patients with oligoprogression after required resistance on immunotherapy in NSCLC. Meanwhile, prospective evaluation or stratified analysis with larger sample size was needed to verify its efficacy and safety in specific group.