Cetuximab efficacy does not vary with EGFR expression

LOS ANGELES-The efficacy of cetuximab (Erbitux) plus chemoradiation in patients with locally advanced non-small-cell lung cancer does not appear to vary with the tumor's epidermal growth factor receptor expression, according to preliminary results of a phase II trial presented at ASTRO 2007 (abstract 101).

Lead author Ritsuko Komaki, MD, of M.D. Anderson Cancer Center, presented the findings of the EGFR analysis from the RTOG 0324 trial. In this study, patients with stage III NSCLC received cetuximab during week 1; combined paclitaxel, carboplatin, cetuximab, and radiation therapy (63 Gy) during weeks 2 through 8; cetuximab during weeks 9 through 11; and, finally, paclitaxel, carboplatin, and cetuximab during weeks 12 through 17. Median follow-up is 17.6 months.

Although the protocol did not require tissue collection, 51 of the 87 enrolled patients (59%) had evaluable tissue for EGFR analysis. Patients who had evaluable tissue had a marginally higher prevalence of squamous histology than their counterparts without such tissue (41% vs 22%) but were otherwise similar.

"The patients with EGFR data evaluable were a favorable subset," she said. Relative to their counterparts who did not have tissue for analysis, patients who did had significantly better overall survival (69% vs 34%, HR 2.25) and were significantly less likely to experience a failure (49% vs 64%, HR 1.97) by 18 months.

Among the patients evaluated for EGFR, the median Quik Score (mean optical density staining index/100) was 0.652 (range, 0 to 0.99). Compared with patients with scores at or below the median, patients with above-median scores were marginally more likely to be male (72% vs 46%) and less likely to have stage IIIB disease (44% vs 69%).

However, outcomes did not differ by Quik Score: Patients with above-median scores, and patients with lower scores had essentially the same 18-month rates of overall survival (60% vs 77%) and failure (53% vs 46%).

"The take-home message from this EGFR analysis is that it is critical to collect tissue samples to help us identify which patients will get more benefit from EGFR inhibitors in this setting," she said.

If the 2-year results of the trial overall are promising (and 1.5-year data do indeed suggest median survival will exceed 22 months), that would support a proposed prospective randomized phase III trial comparing chemoradiation with and without cetuximab, she concluded.