CHICAGO – The clear advantage goes to the second-generation tyrosine kinase inhibitor in a new trial comparing dacomitinib to gefitinib for advanced non–small cell lung cancer.
In a randomized, open-label phase III trial designed as a head-to-head comparison of the two drugs for the first-line treatment of advanced non–small cell lung cancer (NSCLC), “the blinded, independent review showed that we have a median progression-free survival (PFS) of 14.7 months versus 9.2 months,” said first author Tony Mok, MD, professor and chair of the department of clinical oncology at the Chinese University of Hong Kong. This PFS rate, he said, “is among the highest of randomized phase III trials in the first-line setting.”
Two years into the study, those taking dacomitinib had triple the PFS rate of those on gefitinib (30.6% versus 9.6%). The overall hazard ratio (HR) for PFS with dacomitinib compared to gefitinib was 0.59 (95% confidence interval [CI], 0.47-0.74, P less than .0001).
A previous single-arm phase II trial of the drug, ARCHER 2017, showed a response rate of 75.6% and a median PFS of 18.2 months for patients with NSCLC and an EGFR-activating mutation.
“Based on these data, we thought it was likely that we could have a hypothesis for dacomitinib to be superior to gefitinib, a first-generation TKI [tyrosine kinase inhibitor], in terms of progression-free survival,” Dr. Mok said in a press conference at the annual meeting of the American Society of Clinical Oncology. Dacomitinib is a second-generation TKI.
Patients in the new study, ARCHER 1050, had advanced NSCLC with EGFR-activating mutations and no prior systemic treatment for their advanced disease. In addition, patients had good performance status, could not have had prior TKI exposure, and could not have CNS metastases. This last exclusion, explained Dr. Mok, was because investigators were uncertain about dacomitinib’s CNS penetration at the time of study design, and because gefitinib may also not be the best therapeutic choice for CNS metastases.
Patients were randomized 1:1 to receive either dacomitinib 45 mg orally daily (n = 227), or gefitinib 250 mg orally daily (n = 225). Patients were stratified by whether or not they were ethnically Asian, and by whether they had EGFR mutation of exon 19 or exon 21. Patients were balanced in terms of age, gender, ethnicity, smoking, and performance status between arms. About 75% of the patients were Asian, and 65% were nonsmokers.
The international study enrolled patients from 71 centers in Asia and Europe. At the time of the data cutoff, investigators saw PFS events totaling 59.9% in the dacomitinib arm and 79.6% in the gefitinib arm. Patients were followed for PFS for a median of 22.1 months. “We have relatively mature data,” said Dr. Mok, except for overall survival, with only 36.9% of events occurring at the time of the data cutoff.
The primary endpoint in the open-label trial was PFS in the intention-to-treat population, as assessed by an independent, blinded reviewer. Dr. Mok said that the study was powered to see at least 256 PFS events, and to see an improvement in PFS for dacomitinib that equated to an HR of no more than 0.667. This would translate to median PFS for dacomitinib of 14.3 months versus 9.5 months for gefitinib, values Dr. Mok said were “reasonable.” And, he pointed out, the study results fell almost exactly in line with these predictions, though the actual HR was a bit lower than predicted.
An analysis of PFS by subgroup, also conducted by independent review, found that dacomitinib was favored for all subgroups except for non-Asian patients, for whom the HR was 0.89 but did not reach statistical significance. Since these patients made up about one-fourth of the study population, said Dr. Mok, small sample size was a potential issue. “But we have to ask ourselves the question, do they really perform worse than the Asians, if they have a response?”
To attempt to answer this question, the investigators performed an exploratory analysis of the 72 non-Asian patients who had responded to therapy. Among this group, they saw data similar to that of the overall group, with an HR of 0.547 (95% CI, 0.321-0.933, P less than .0123).
Secondary endpoints included investigator-assessed PFS, overall survival, objective response rate, duration of response, quality of life, and safety assessments.
Objective response rates were similar between arms, at 74.9% for dacomitinib and 71.6% for gefitinib (P = .3883). However, the median duration of response was significantly longer for those on dacomitinib (14.8 versus 8.3 months, P less than .0001).
“This may be best explained by looking into the depth of the response,” said Dr. Mok. Patient-level data showed that dacomitinib patients had a larger reduction in target lesion size; “this may reflect a more potent inhibition of EGFR,” he said.
With the more potent inhibition, however, came more frequent grade 3 adverse events involving diarrhea, dermatitis, stomatitis, and paronychia for those on dacomitinib; however, noted Dr. Mok, serious transaminase elevations were more common in the gefitinib group. “There is no new signal” for concerning toxicity, he said. Dose reductions were more common in dacomitinib than in gefitinib (66.1% versus 18%), but there are two tiers of dose reductions permissible with dacomitinib, giving some flexibility.
Dr. Mok reported financial relationships with multiple pharmaceutical companies, including Pfizer and SFJ Pharmaceuticals, which sponsored the study.
On Twitter @karioakes