Phase II trial of clinical activity and safety of ceritinib combined with stereotactic ablative radiotherapy (SABR) in lung adenocarcinoma patients.

Abstract

e21571 Background: ALK -targeting drugs and SABR are combined in patients with metastatic cancer, anecdotally yielding clinical benefit. However, the precise impact of the combination and the optimal time to introduce SABR remain unknown. Methods: This completed phase 2 study (NCT02513667) had a primary objective of doubling progression free survival (PFS) for ALK+ lung adenocarcinoma patients by consolidating all remaining disease with SABR, 8-10 weeks after ceritinib initiation. Patients who then progressed could receive repeat SABR as long as they then resumed ceritinib. Patients were divided into ALK-inhibitor naïve vs previously treated cohorts. Oligometastatic disease was NOT a requirement for study entry, CNS disease was permitted. Blood was serially analyzed for variation in 1. blood cfDNA detection of resistance mechanisms 2. flow cytometric analysis of white cell populations. Results: 14 patients were enrolled out of a planned 33; 7 female; 3 hispanic/latino; median age was 53 years (range 31-78); 5 patients had previously received crizotinib. 4 patients stopped ceritinib within 30 days due to toxicity, despite dose reductions or with-food administration. However, all patients still completed initial SABR consistent with protocol time-points. Patients predominantly had thoracic disease irradiated (11/14, 78%). Two patients had only brain metastases treated and 1 had bone only metastases treated. 4 had one fraction SBRT regimens (16-24 Gy per fraction) delivered to disease, 3 had three fraction SBRT regimens (9-11 Gy per fraction) delivered to disease, and 7 had five fraction SBRT or 15 fraction hypofractionated regimens (6 Gy per fraction or 3Gy per fraction, respectively) delivered to disease. Disease control in all irradiated areas was 100%. There was no significant grade 3 or higher toxicity associated with radiation. Broad variability in baseline and serial levels of circulating PMN-MDSC, VEGFR2, FoxP3+, CD56+CD16+ and various T-cell populations showed no clinical correlation. The trial terminated early due to increased use of alternative targeted therapies, thus the primary endpoint was not met. 8 patients had CR/PR/SD as best response. Including those who did not tolerate ceritinib, median PFS was 12 months, max of 31 months with 1 ongoing response. Conclusions: Consolidative SABR after ALK therapy is well tolerated, can be repeated and may prolong PFS compared to drug alone. Ceritinib toxicity meant higher rates of discontinuation but this did not prevent consolidative SABR in any patient. Clinical trial information: NCT02513667.