Treatment for EGFR-Mutant Lung Cancer Is Rapidly Expanding
There has been a “renaissance” in the treatment strategies of patients with non-small cell lung cancer (NSCLC) who have EGFR-mutation–positive disease, Edward S. Kim, M.D.
“It has been gratifying to see the change that has occurred since the early 2000s and late 1990s,” said Kim, who is chair of Solid Tumor Oncology and Investigational Therapeutics and the Donald S. Kim Distinguished Chair for Cancer Research at the Levine Cancer Institute, Carolinas HealthCare System. “The closer we get to 2020, [we learn] the ways we can help patients with our different tests.”
In an era where immunotherapy is becoming the new cornerstone in the field, Kim added, comprehensive gene panels are able to detect molecular biomarkers—EGFR, ALK, ROS1, PD-L1 or BRAF—that can guide treatment. In EGFR-mutant NSCLC, the standard frontline tyrosine kinase inhibitor (TKI) choices include Gilotrif (afatinib), Tarceva (erlotinib) and Iressa (gefitinib).
“All [three EGFR inhibitors] target the L858R mutations but, as we have seen over time, there have been some differences with these drugs,” said Kim. “There have been subsets pulled out; it’s no longer just EGFR. There are specific mutations that exist within this family and we're going to have to know what [drugs] work better with what [mutations].”
When the third-generation EGFR TKI Tagrisso (osimertinib) entered the landscape, it was explored in comparison to pemetrexed in the AURA3 trial for patients who progress on a first-line EGFR inhibitor and harbor the T790M resistance mutation.
“When this drug was first tested, we saw tremendous activity to the resistance mutation T790M,” Kim recalled. “What a strategy — you could start someone with an EGFR TKI who had a sensitizing mutation that would do well for a long time and then, eventually, the drug would stop working, the tumors would start growing, you do a biopsy, you find T790M in about half of those patients — and then you give them another pill. Theoretically, you could treat a lung cancer patient who is fortunate to have these mutations for quite some time. It has been shown that if you look at osimertinib versus chemotherapy in T790M-positive patients, it is better than chemotherapy.”
Outside of the three EGFR TKIs approved in the frontline setting, the EGFR-mutant NSCLC paradigm transformed in September 2017 with the phase 3 FLAURA findings at the 2017 European Society of Medical Oncology (ESMO) Congress. Here, the oncology community saw the magnitude of benefit with the use of frontline Tagrisso when compared with either Iressa or Tarceva in patients with EGFR-mutant NSCLC.
Results of FLAURA showed that frontline Tagrisso was associated with a 54 percent reduction in the risk of progression or death versus standard therapy, which included Tarceva or Iressa. Additionally, the median progression-free survival (PFS) was 10.2 months for standard therapy and 18.9 months with Tagrisso. The median duration of response was doubled with Tagrisso versus standard therapy at 17.2 and 8.5 months, respectively.
“It was pretty impressive PFS; it has convinced most of the lung cancer community that, when it becomes approved, it will become a first-line treatment,” Kim said. “Osimertinib is the new standard for 2017 based on these frontline data; it’s not approved yet there but I know people are going to be using it.”
Though overall survival data remain immature, there is an encouraging trend that favors Tagrisso yet it is not yet statistically significant. A P value of less than .0015 was required for statistical significance at 25 percent maturity.
Additionally, the trial’s findings highlighted a benefit with Tagrisso in patients who also had brain metastases. In those with central nervous system (CNS) disease evaluable for response (46 patients), CNS overall response rate (ORR) was 70 percent with Tagrisso compared with 31 percent for patients treated with platinum-based doublet chemotherapy. Across the full population (416 patients), CNS PFS also favored the Tagrisso group at 11.7 months versus 5.6 months.
The CNS activity with Tagrisso in EGFR-mutation–positive NSCLC mimics that of the ALK inhibitor Alecensa (alectinib) in ALK-positive NSCLC, Kim explained.
“We are going to hit a point where we have drugs like alectinib, which has a very similar profile in ALK, and osimertinib, and you’re not going to need that radiation oncology consult if you find brain metastases on your staging MRI,” said Kim. “I would even argue that, if you tested for the biomarkers and found EGFR or ALK, and the patient was a good candidate for either of these drugs, you don’t even need the MRI right away…you know it’s going to [spread to] that area. I foresee we are not going to need that down the road; it will be a little bit of a practice change, and it will take some time.”
Safety findings with Tagrisso and Iressa / Tarceva in FLAURA were found to be generally similar in FLAURA. Tagrisso was associated with less dermatitis acneiform – a type of skin lesion (25 percent vs 48 percent), less AST elevation (9 percent vs 25 percent) and less ALT elevation (6 percent vs 27 percent). Moreover, there was a lower incidence of any-cause grade 3/4 adverse event with Tagrisso (34 percent vs 45 percent).
Kim stated that the FLAURA data demonstrate that Tagrisso should now be the frontline standard of care for EGFR-mutated patients.
For patients who develop resistance to Tagrisso, an identified mutation is C797S. Anecdotally, Kim added, first-generation EGFR TKIs have been found to help treat this resistance.
However, Gilotrif is showcasing potential in patients with more uncommon EGFR mutations. In October 2017, the FDA granted a priority review to a supplemental new drug application for Gilotrif for the frontline treatment of those with metastatic NSCLC whose tumors harbor EGFR exon 21 (L861Q), G719X or S768I substitution mutations. These types of mutations represent less than 10 percent of the EGFR mutations found in patients with NSCLC, but are associated with poor prognosis and survival.
“This is an area that is a gap and, if [a patient] gets one of those, afatinib is a very reasonable choice and we haven’t seen any other data from any other TKI,” Kim explained.
Additionally, Kim emphasized the need for tissue testing to accurately diagnose and stage lung cancer and that patients should not be treated with chemotherapy without having biomarker data.
“It makes me very happy to say that lung cancer is the model for precision medicine right now in almost 50 percent of our patients with NSCLC—it can be covered by some sort of mutation or aberration, such as PD-1 expression, EGFR, ALK, BRAF and ROS1. This is all giving great hope for patients and that’s what makes it very gratifying.”