Shortly after osimertinib was approved for patients with non–small cell lung cancer in 2020 by the Food and Drug Administration, a patient came to me with increasing shortness of breath. He had been on erlotinib (Tarceva) for about 2 years and had done well. Nearly all of his pulmonary lesions had resolved and he was feeling well. He enjoyed boating in the summer and visiting grandkids in California in the winter. However, on this day, it was different. He was losing weight; he was tired and didn't feel strong enough to put his boat in the water that spring. Long story short: We ordered a CT scan and all of his lesions were progressing. Since osimertinib had just been approved, we got a second biopsy, hoping that his insurance would pay for it. It did and sure enough, a new T790M mutation was present. He was on osimertinib for another 2 years before progressing and starting chemotherapy.
Second Biopsies Increasingly Routine
The practice of ordering a second biopsy for patients with non–small cell lung carcinoma (NSCLC) was not common practice until after 2015 when the Food and Drug Administration approved gefitinib, a tyrosine kinase inhibitor (TKI) for patients whose tumors have epidermal growth factor receptor (EGFR) exon 19 deletions or exon 21 (L858R) substitution mutations.
Up until then, second biopsies were not routinely done for lung cancers. But with the advent of targeted therapy and new drugs designed specifically to tackle first- and second-line treatment resistance mutations, rebiopsies have become a necessity for patients with progressive disease.
Epidermal growth factors, including HER2, ErbB2, and MET, are receptors of tyrosine kinases that control cell growth, but when in overdrive, they can lead to the development of cancers, including lung adenocarcinoma, conventional glioblastoma multiforme, glioblastoma, colon adenocarcinoma, and NSCLC.
EGFRs date back to 1962 with their discovery by Stanley Cohen. The discovery was so important that in 1986, Mr. Cohen was awarded the Nobel Prize in physiology or medicine for the discovery along with Rita Levi-Montalcini.
Now, many years later, we finally have a string of new approvals for mutations in the EGF family of receptors and several under study.
The more commonly used strategy for blocking EGFR signaling in lung cancer is the use of tyrosine kinase inhibitors, which compete with adenosine triphosphate (ATP) for binding to the tyrosine kinase portion of the receptor. They are located at chromosome 7p11.2. The most frequent mutations that sensitize patients to EGFR inhibitors include exon 19 deletions and L858R point mutation in exon 21, although multiple other driver mutations also exist.
The first-generation of EGFR TKIs include gefitinib and erlotinib, which bind reversibly to the EGF receptor. Second-generation inhibitors afatinib and dacomitinib bind irreversibly. Osimertinib, a third-generation EGFR TKI, which also binds irreversibly, was approved in 2020 for adjuvant therapy, and first- and second-line treatment in patients with NSCLC who have EGFR mutation–positive disease.
First-Generation EGFR Tyrosine Kinase Inhibitors
Four randomized, first-line, placebo-controlled phase 3 trials conducted with EGFR TKIs in combination with platinum-based doublet chemotherapy in an EGFR nonselected patient population failed to show a survival benefit with erlotinib or gefitinib (TRIBUTE, Tarceva Lung Cancer Investigation Trial, INTACT 1, INTACT 2).
However, a first-line study randomized patients to gefitinib or chemotherapy with carboplatin-paclitaxel, and included patients with or without an EGFR mutations. In the subgroup of patients with an EGFR mutation, progression-free survival (PFS) was significantly longer among those who received gefitinib than among those who received carboplatin–paclitaxel (hazard ratio for progression or death, 0.48), whereas in the subgroup of patients who were negative for the mutation, PFS was significantly longer among those who received chemotherapy (HR for progression or death with gefitinib, 2.85).
Numerous studies have shown that EGFR TKIs used in the first-line setting improved progression free survival, response rates, and quality of life while reducing toxicity. A recent meta-analysis of randomized clinical trials involving EGFR TKIs showed that EGFR TKI improved PFS with a HR of 0.40, compared with standard chemotherapy with fewer serious adverse events, although no benefit on overall survival was observed (HR, 0.96; 95% confidence interval, 0.83-1.10; P = .556).
T790M: The Most Common Resistance Mutation
T790M is the most common resistance mechanism to develop in patients with EGFR mutations being treated with EGFR TKIs. A randomized phase 3 trial of osimertinib vs. chemotherapy in patients with T790M-positive advanced NSCLC who had disease progression after first-line EGFR-TKI therapy, reported a median duration of progression-free survival that was significantly longer with osimertinib than with platinum therapy plus pemetrexed (10.1 months vs. 4.4 months; HR, 0.30). In addition, among 144 patients with metastases to the central nervous system, the median duration of PFS was longer among patients receiving osimertinib than among those receiving platinum therapy plus pemetrexed (8.5 months vs. 4.2 months; HR, 0.32). However, now that osimertinib has moved into the front-line setting, it has left a void for the treatment of patients with advanced disease who have failed osimertinib.
New Resistance Mechanisms Continue to Be Identified
One of the most common sets of resistance mutations are insertions in exon 20 of the EGF receptor gene. These are a heterogenous group of mutations, many of which do not respond to first-, second-, or third-generation TKIs. Some, such as EGFR-A763_Y764insFQEA, may be sensitive to first- and third-generation EGFR TKIs. Other drugs targeting exon 20 insertion mutations are under development.
Newly approved by the FDA within the last year are mobocertinib and CLN-081 for adult patients with locally advanced or metastatic NSCLC with EGFR exon 20 insertion mutations.
Savolitinib is a receptor tyrosine kinase (MET) inhibitor currently under development for NSCLC and other cancers. Amivantamab-vmjw was approved by the FDA last year for metastatic NSCLC. It targets EGF and MET receptors in patients with EGFR exon 20 insertion mutations.
We finally have approved drugs for exon 20 insertions and c-Met amplification, even though their approvals are based on small, single arm studies with no definitive claims of improved efficacy over older therapies. Taking a second biopsy will help determine which resistance mechanisms are active to better identify subsequent treatment as in my patient described in this article.
Schiller is a medical oncologist and founding member of Oncologists United for Climate and Health. She is a former board member of the International Association for the Study of Lung Cancer and a current board member of the Lung Cancer Research Foundation.
This article originally appeared on MDedge.com, part of the Medscape Professional Network.
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Cite this: In Progressive Lung Cancer Second Biopsies May Be the Norm Now - Medscape - Oct 05, 2022.