Efficacy and safety of dose-escalated alectinib in patients with metastatic ALK-positive NSCLC and CNS relapse on standard dose alectinib.

Abstract

e21079 Background: Central nervous system (CNS) metastases represent a common cause of morbidity and mortality in patients (pts) with ALK-positive (ALK+) non-small cell lung cancer (NSCLC), with limited therapeutic options. We previously reported re-induction of CNS responses using dose intensification of alectinib in two pts with metastatic ALK+ NSCLC who had experienced CNS progression on standard dose alectinib. However, this strategy has not been assessed in larger cohorts. Methods: In this retrospective study, pts were eligible if they had advanced ALK+ NSCLC with CNS relapse on standard dose alectinib (600 mg twice daily) and subsequently received dose-escalated alectinib (900 mg twice daily). Medical records and radiographic imaging were reviewed to determine treatment outcomes. CNS efficacy was assessed per the modified Response Evaluation Criteria in Solid Tumors version 1.1. Treatment-related adverse events (trAEs) were graded per the CTCAE version 5.0. Results: 27 pts were eligible [male, 67%; median age at diagnosis, 53 (range, 31-69)]. Pts had previously received median 3 lines of systemic therapy (range, 1-12) and median 2 ALK TKIs (range, 1-4); all had received standard dose alectinib with CNS progression. 19 pts (70%) had received prior CNS-directed radiotherapy (RT) [median time from most recent RT to dose-escalated alectinib, 13.9 months (mos) (range, 0.2-52.3)]. The median duration of dose-escalated alectinib therapy in this cohort was 7.7 mos (95% CI, 4.8-10.9), with median overall progression-free survival (PFS) of 7.8 mos (95% CI, 4.9-13.7). Among 25 response-evaluable pts with baseline measurable or non-measurable CNS metastases, the CNS objective response rate (ORR) was 8.0% (95% CI, 1.0-26.0), with 2 pts having intracranial complete responses. CNS disease control rate (DCR) was 92.0% (95% CI, 74.0-99.0), with median CNS duration of response (DoR) of 5.3 mos (95% CI, 3.4-8.3) and median CNS PFS of 7.1 mos (95% CI, 4.4-13.7). Of 3 patients with baseline measurable CNS disease, all 3 had best intracranial response of SD, and median CNS PFS was 6.7 mos (95% CI, 6.2-not reached). Dose-escalated alectinib was well tolerated with no drug discontinuation due to trAE and no grade 3 or higher trAEs. One pt required dose reduction to 750 mg twice daily due to intolerable grade 2 fatigue. 23 pts (85%) experienced grade 1-2 trAEs. Grade 1-2 trAEs that occurred in 10% of pts were anemia (52%), fatigue (37%), constipation (26%), bilirubin increase (15%), alkaline phosphatase increase (15%), and peripheral neuropathy (11%). Conclusions: Dose intensification of alectinib demonstrated meaningful efficacy and tolerability in pts with metastatic ALK+ NSCLC who had experienced CNS disease relapse on standard dose alectinib, and may represent a viable therapeutic option for re-establishing CNS disease control.