Three-arm randomized phase II study of cisplatin and etoposide (CE) versus CE with either vismodegib (V) or cixutumumab (Cx) for patients with extensive stage-small cell lung cancer (ES-SCLC) (ECOG 1508).

Abstract

7508 Background: Targeted inhibition of the Hedgehog (HH) pathway by V & Insulin-like Growth Factor type-1 Receptor (IGF-1R) by Cx enhances efficacy of chemotherapy, and also demonstrates activity against the tumor cell fraction responsible for disease recurrence in SCLC. Methods: Patients (Pts) with newly diagnosed ES-SCLC with measurable disease, ECOG PS 0-1 were randomized to receive (four 21-day cycles) CE alone [(C 75 mg/m2 D1 & E 100 mg/m2 D1-3) Arm A] or in combination with either V [(150 mg/day PO) Arm B] or Cx [(6mg/kg weekly IV) Arm C]. Pts with responsive or stable disease on Arms B & C were continued on V or Cx respectively until disease progression or unacceptable toxicity. The primary endpoint was progression-free survival (PFS), stratified on gender. Circulating tumor cells (CTCs) were isolated/enumerated by Veridex Cell Search Platform at baseline, after 1or 2 cycles of chemotherapy, at completion of 4 cycles & 3 months (m). thereafter for correlation with efficacy parameters. The study was designed to detect a PFS HR of 0.58 with 90% power & an overall one-sided type I error rate of 0.10 for each of the comparisons of the V and Cx arms to CE alone. Results: 155 eligible pts were treated; 136 have died & 149 have experienced a PFS event. Pt. demographics & disease characteristics are well-balanced between the three arms except higher rate of PS 0 on Arm B (p=0.03). The median PFS on Arms A, B & C are 4.7, 4.4 & 4.6 m, the median OS 9.1, 9.8 & 10.1 m, & the RR are 43%, 52% & 49% respectively. None of the comparisons of these outcomes are statistically significant. PFS HR for V+CE vs. CE: 1.32, p=0.21, and for Cx+CE vs. CE: 1.12, p=0.58. The median OS among those with low CTC count (≤100 per 7.5ml) at baseline is 10.7 m vs. 7.2 m for those with high CTC count [HR1.70, p=0.01]. Toxicities in all three arms are as expected with the combination of CE alone. Conclusions: There is no significant improvement in PFS or OS with the addition of either V or Cx to CE vs.CE alone in pts with ED-SCLC. Low baseline CTC count is associated with improved OS, suggesting its role as a prognostic biomarker in SCLC. Clinical trial information: NCT00887159.