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  P3.02 - Poster Session 3 - Novel Cancer Genes and Pathways (ID 149)

  • Event: WCLC 2013
  • Type: Poster Session
  • Track: Biology
  • Presentations: 1
  • Moderators:
  • Coordinates: 10/30/2013, 09:30 - 16:30, Exhibit Hall, Ground Level

  • 12395

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    P3.02-009 - <b>ROR1 as a novel therapeutic target for EGFR-mutant non-small-cell lung cancer (NSCLC) patients with the EGFR T790M mutation</b> (ID 1395)

    09:30 - 09:30  |  Author(s): R. Estrada-Tejedor
    • Abstract

    Background
    Molecular cross-talk between EGFR and other signaling pathways creates alternative means of tumor cell proliferation and promotes resistance to single-agent erlotinib therapy in NSCLC driven by EGFR mutations. ROR1 knockdown inhibited the growth of NCI-H1975 cells (harboring EGFR L858R and T790M mutations). A pro-survival function for ROR1/MEK/ERK signaling in cooperation with AKT has been demonstrated. We have assessed ROR1 expression in 45 patients from the EURTAC trial (clinicaltrials.gov NCT00446225), 27 of whom harbored pretreatment concomitant EGFR T790M mutations, and correlated results with outcome.

    Methods
    ROR1 mRNA expression was examined by quantitative RT-PCR and categorized by terciles; patients were classified as having low/intermediate or high ROR1 expression. The T790M mutation was determined by Taqman with a PNA to inhibit amplification of the wild-type (wt) allele. Tumor samples were run in octuplicates; this method can detect 1 mutated allele among 10,000 wt alleles.

    Results
    Median age 65; 68.9% female; 57.8% never-smokers; 95.6% ECOG PS <2; 91.1% adenocarcinoma; 68.9% exon 19 deletion. No differences in baseline characteristics were observed according to ROR1 expression levels. 24 patients (53.3%) were treated with erlotinib and 21 (46.7%) with chemotherapy. 10 (41.7%) erlotinib-treated patients and 6 (28.6%) chemotherapy-treated patients had high ROR1 mRNA levels. Among erlotinib-treated patients, response rate (RR) was 40% for the 10 patients with high ROR1 levels vs 71.4% for the 14 with low/intermediate levels (P=0.058). Among chemotherapy-treated patients, RR for the 15 patients with low/intermediate ROR1 levels was 6.7%; the 6 patients with high ROR1 levels did not respond. Progression-free survival (PFS) was 11.8 months (m) for erlotinib-treated patients with low/intermediate ROR1 levels vs 5.8 m for those with high levels. PFS for chemotherapy-treated patients was 5.6 and 9 m, respectively (P=0.0165). 15 erlotinib-treated patients harbored concomitant T790M mutations; for these patients, PFS was10.8 m for those with low/intermediate ROR1 levels vs 2.7 m for those with high levels (P=0.0138).

    Conclusion
    ROR1 expression has a differential effect on outcome to erlotinib and chemotherapy in EGFR-mutant NSCLC patients. High ROR1 expression significantly limits PFS in erlotinib-treated patients with T790M mutations and ROR1-directed therapies can enhance the efficacy of treatment. In contrast, high ROR1 expression confers longer PFS to chemotherapy in the same group of patients. The role of chemotherapy and erlotinib in EGFR-mutant NSCLC patients with high ROR1 expression warrants further investigation.