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MO18 - NSCLC - Targeted Therapies IV (ID 116)
- Event: WCLC 2013
- Type: Mini Oral Abstract Session
- Track: Medical Oncology
- Presentations: 1
MO18.12 - Impact of <em>KRAS</em> codon sub-types in a Phase II second-line trial in <em>KRAS</em>-mutant advanced non-small cell lung cancer (NSCLC) of selumetinib plus docetaxel versus docetaxel alone (ID 3331)
16:15 - 17:45 | Author(s): G. Jeannin
Phase II data from patients with KRAS mutation-positive NSCLC, selumetinib (AZD6244, ARRY-142886) plus docetaxel showed promising efficacy versus placebo plus docetaxel alone (Jänne et al. Lancet Oncol 2013;14:38–47). Median OS was 9.4 months (95% CI 6.8–13.6) in the selumetinib group and 5.2 months (95% CI 3.8–non-calculable) in the placebo group (HR for death 0∙80, 80% CI 0.56–1.14; one-sided p=0.21). Median PFS was 5.3 months (95% CI 4.6–6.4) and 2.1 months (95% CI 1.4–3.7), respectively (HR for progression 0∙58, 80% CI 0.42–0.79; one-sided p=0.014). 37% of patients in the selumetinib group and 0% in the placebo group had an objective response (two-sided p<0.0001). The KRAS mutation codon subtype might impact on prognosis and/or response to therapy. The BATTLE trial suggested that G12V or C KRAS mutations confer relatively poorer outcome within the KRAS mutant NSCLC sub-type (Ihle et al. J Natl Cancer Inst 2012;104:228–39). In cell lines carrying these codons, Akt phosphorylation but not ERK phosphorylation was low compared with other codons, suggesting these codons might confer greater dependence upon MEK/ERK signaling. We sought to understand if any codons or combinations of codons selected for striking treatment effects either between or within treatment groups in the Phase II study.
Post-hoc analysis explored the hypotheses that patients whose tumours carried G12C or G12V KRAS mutations would have a worse prognosis and that these patients would have a better outcome with the addition of selumetinib. Clinical benefit was measured by PFS, OS and ORR.
G12V or G12C mutations were present in 57% of patients and whilst not reaching statistical significance, trends for PFS, OS and ORR support the hypothesis (see table, PFS). Patients with G12V mutations responded better to selumetinib plus docetaxel than other patients as measured by change in tumour size at week 6 (G12V=-62%, G12C=-8%, G12D=+3%, reduction across all codons=-18%; two sided p=0.007). It is therefore possible that trends supporting the primary hypothesis were driven by effects in the small number of G12V codons (n=9). Table. Summary of analysis of progression-free survival (PFS): MITT by mutation subgroup
Subgroup Selumetinib + docetaxel, n (number of PFS events) Docetaxel, n (number of PFS events) Selumetinib + docetaxel vs docetaxel, PFS HR (80% CI) G12C or G12V 24 (18) 23 (21) 0.48 (0.31–0.74) Other 19 (17) 17 (15) 0.72 (0.44–1.16) Overall 43 (35) 40 (36) 0.58 (0.42–0.79)
Any impacts of codon sub-type on the treatment effect in this trial were not sufficiently significant to be detected in this small Phase II trial of 87 patients, but the trends observed in this retrospective subgroup analysis warrant monitoring of the impact of specific codons or groups of codons in future clinical trials.