Association of depth of target lesion response to brigatinib with outcomes in patients with ALK inhibitor-naive ALK+ NSCLC in ALTA-1L.

9072 Background: In patients (pts) with crizotinib (CRZ)-refractory advanced ALK+ NSCLC in the phase 2 ALTA trial (NCT02094573), the depth of target lesion response to brigatinib (BRG) correlated with PFS and OS. Here, we examine the association of maximum decrease in target lesions with PFS and OS in ALTA-1L (NCT02737501), a randomized phase 3 trial of BRG vs CRZ in pts with ALK inhibitor-naive advanced ALK+ NSCLC. Methods: Pts were randomized 1:1 to receive BRG 180 mg qd (7-day lead-in at 90 mg; n=137) or CRZ 250 mg bid (n=138). Pts with target lesion assessment by blinded independent review committee (BIRC) were grouped based on greatest decrease from baseline per RECIST v1.1: none–50%, 51%–75%, and 76%–100% shrinkage. Outcomes in the ≤50% target lesion shrinkage group served as the comparator for outcomes in the 51%–75% and 76%–100% groups. Results: At study end (last pt contact: Jan 29, 2021), 124/137 pts in the BRG arm and 125/138 pts in the CRZ arm had ≥1 evaluable target lesion assessment; female (BRG/CRZ), 51%/59%; median age, 57.5/60.0 years. Median follow-up was 40.8/15.7 months. In BRG/CRZ arms, 76%-100% shrinkage was observed in 56%/34% of pts, 51%-75% shrinkage in 27%/30%, and ≤50% shrinkage in 16%/35%, respectively. BRG was associated with significantly more pts with target lesion shrinkage >75% vs CRZ ( P=0.0005), and a Cochran-Armitage trend analysis demonstrated significantly deeper response across all shrinkage groups for BRG compared with CRZ ( P<0.0001). A majority of pts in the BRG arm experienced 76%–100% target lesion shrinkage in all subgroups analyzed. Pts treated with BRG or CRZ with target lesion shrinkage >50% had lower risk of a PFS event (BRG HR [95% CI]: 51%–75% shrinkage, 0.58 [0.29–1.18]; 76%–100%, 0.23 [0.12–0.46]; CRZ: 51%–75% shrinkage, 0.68 [0.41–1.12]; 76%–100%, 0.26 [0.15–0.45]) or an OS event (BRG: 51%–75% shrinkage, 0.39 [0.17–0.89]; 76%–100%, 0.15 [0.07–0.35]; CRZ: 51%–75% shrinkage, 0.43 [0.21–0.85]; 76%–100%, 0.23 [0.10–0.50]) than pts with ≤50% shrinkage. Longer median time to PFS and OS and higher 4-year estimated OS rates were associated with depth of response in both arms (Table). Conclusions: In this exploratory post hoc analysis, BRG demonstrated significantly deeper target lesion response vs CRZ. Pts with >75% shrinkage had significantly reduced risk of a PFS or OS event vs pts with ≤50% target lesion shrinkage. Clinical trial information: NCT02737501. [Table: see text]