During a presentation at the 16th Annual Winter Lung Conference, Gregory J. Riely, MD, PhD, discusses how oncologists can differentiate between the many EGFR TKIs available for patients with <em>EGFR</em>-mutant non–small cell lung cancer.
Gregory J. Riely, MD, PhD
There are now many EGFR TKIs available for patients withEGFR-mutant nonsmall cell lung cancer (NSCLC), as the treatment landscape continues to evolve. In order to differentiate between these agents, oncologists can look to the spectrum ofEGFRmutations each TKI is targeted to hit, explained Gregory J. Riely, MD, PhD, during a presentation at the 16th Annual Winter Lung Conference™.
All of the EGFR TKIs, first through third generation, are active against the common mutations,EGFRL858R and exon 19 deletion mutations, explained Riely, vice chair of clinical research in the Department of Medicine at Memorial Sloan Kettering Cancer Center. Additionally, both the first- and second-generation agents are all active againstEGFRwild-type, which leads to the common adverse events (AEs) of rash and diarrhea. However, not all are active against T790M mutations,HER2amplification, and beyond.
Afatinib (Gilotrif) demonstrated significant activity in a number of less commonEGFRmutations in an analysis from the LUX-Lung trials, including point mutations in exons 18 through 21 with a confirmed objective response rate of 66% (95% CI, 47%-81%).1Based on these data, afatinib gained an expanded approval in January 2018 for the treatment of patients whose tumors harborEGFRL861Q, G719X, and/or S768I alterations.
Unlike other FDA-approved options, the second-generation agents afatinib and dacomitinib (Vizimpro) both demonstrate activity against HER2, which Riely mentioned could be beneficial, as suggested by data from the ARCHER 1050 trial.
ARCHER 1050 was a randomized phase III trial that compared dacomitinib with the first-generation EGFR TKI gefitinib (Iressa) for the treatment of newly diagnosed patients withEGFR-mutant advanced NSCLC. Patients treated with dacomitinib demonstrated a median progression-free survival (PFS) of 14.7 months (95% CI, 11.1-16.6) compared with 9.2 months (95% CI, 9.1-11.0) with gefitinib (HR, 0.59; 95% CI, 0.47-0.74;P<.0001).2The median overall survival (OS) with dacomitinib was 34.1 months (95% CI, 29.5-37.7) versus 26.8 months (95% CI, 23.7-32.1) with gefitinib (HR, 0.760; 95% CI, 0.582-0.993;P= .0438), according to updated data presented at the 2018 ASCO Annual Meeting.3
Notably, in patients withEGFRexon 21 L858R mutations, dacomitinib also showed an OS benefit compared with gefitinib (32.5 vs 23.2 months; HR, 0.707; 95% CI, 0.478-1.045;P= .0805).
However, treatment with dacomitinib is associated with increased toxicity compared with gefitinib. In ARCHER 1050, grade ≥3 AEs were observed in 63.0% of patients treated with dacomitinib versus in 41.1% of those treated with gefitinib. Dose reductions of dacomitinib were also necessary in 66% of patients compared with 8% of patients who received gefitinib.
“The key way to move forward from first-generation EGFR TKIs is to look at the pattern of resistance to EGFR TKIs,” Riely said. Importantly, only the third-generation inhibitor osimertinib (Tagrisso), though, is effective in targetingEGFRT790M, which is the dominant mechanism of acquired resistance to prior treatment with an EGFR TKI. Riely noted that osimertinib is also active against the commonEGFRL858R and exon 19 deletion mutations, and has slight activity againstEGFRwild-type, which would explain for some of the rash and diarrhea seen in patients treated with this TKI.
“Initial treatment with a third-generation EGFR TKI with the ability to not only inhibit T790M, but also the underlyingEGFRmutation, leads to significantly longer progression-free survival,” Riely said.
In the FLAURA study of osimertinib in the frontline setting compared with standard EGFR TKIs gefitinib and erlotinib, osimertinib demonstrated a median PFS of 18.9 months (95% CI, 15.2-21.4) compared with 10.2 months (95% CI, 9.6-11.1) with erlotinib or gefitinib (HR, 0.46; 95% CI, 0.37-0.57;P<.001). Immature OS data demonstrated a hint of OS benefit compared with standard EGFR TKIs (HR, 0.63; 95% CI, 0.45-0.88;P= .007).4
“Practically, in the clinic, when we’re thinking about this, it helps us in a couple of different ways to start with osimertinib. We don’t have the transition point where we have to biopsy patients to look for T790M and the uncertainty around that. But probably more importantly is the difference in toxicity. Patients who receive osimertinib have a fairly improved toxicity profile compared with patients who receive gefitinib or erlotinib. There’s less rash, [and] there’s less diarrhea,” Riely commented.