IRESSA is indicated for the first-line treatment of patients with metastatic non-small cell lung cancer (NSCLC) whose tumors have epidermal growth factor receptor (EGFR) exon 19 deletions or exon 21 (L858R) substitution mutations as detected by an FDA-approved test
Specifically, Iressa was approved as initial therapy for the treatment of patients with advanced NSCLC with these specific mutations within the EGFR pathway following years of study to determine which EGFR patients benefited from treatment.
The EGFR pathway is involved in cellular replication and spread. If there are mutations within the pathway, spread of cancer can remain uncontrolled. EGFR inhibitors are agents that target specific points along the EGFR pathway. The agents reduce or minimize the spread of cancer cells that have mutations within the EGFR.
The approval of gefitinib was based on the results of a multicenter, single-arm, open-label clinical study of a total of 106 treatment naïve-patients with metastatic EGFR mutation positive NSCLC who received gefitinib at a dose of 250 mg daily until disease progression or intolerable toxicity. The major efficacy outcome was objective response rate (ORR) according to RECIST v1.1 as evaluated by both a Blinded Independent Central Review (BICR) and investigators. The BICR ORR was 50% (95% CI: 41, 59) with a median duration of response (DoR) of 6.0 months. Investigator-determined ORR was 70% (95% CI: 61, 78) with a median DoR of 8.3 months.
Efficacy results were supported by an exploratory analysis of a subset of a randomized, multicenter, open-label trial conducted in patients with metastatic adenocarcinoma histology NSCLC receiving first-line treatment. Patients were randomized (1:1) to receive gefitinib 250 mg once daily or up to 6 cycles of carboplatin/paclitaxel. The efficacy outcomes included progression-free survival (PFS) and ORR as assessed by the BICR. The subset population consisted of 186 of 1217 patients (15%) determined to be EGFR positive and had radiographic scans available for a retrospective assessment by a BICR. In this subset, there were 88 gefitinib-treated patients and 98 carboplatin/paclitaxel-treated patients. The hazard ratio for PFS in the gefitinib-treated arm was 0.54 (95% CI: 0.38, 0.79) with a median PFS of 10.9 months for the gefitinib-treated patients and 7.4 months for the carboplatin/paclitaxel-treated patients as assessed by BICR. In addition, the BICR ORR was 67% (95% CI: 56, 77) with a DoR of 9.6 months for gefitinib-treated patients and 41% (95% CI: 31, 51) with a DoR of 5.5 months for carboplatin/paclitaxel-treated patients.
Serious and uncommon adverse drug reactions were evaluated in 2462 patients with NSCLC who received gefitinib monotherapy in three randomized clinical studies. Significant adverse reactions were interstitial lung disease, which occurred in 1.3% of patients, fatal hepatotoxicity which occurred in 0.04% of patients, and grade 3 ocular disorders which occurred in 0.1% of patients.
The approval of Iressa is “intended for the treatment of patients whose tumors express the most common types of EGFR mutations in NSCLC (exon 19 deletions or exon 21 L858R substitution gene mutations). The therascreen EGFR RGQ PCR Kit was approved as a companion diagnostic test to identify patients with tumors having the EGFR gene mutations in order to determine which patients would be appropriate for treatment with Iressa,” according to a press release by the U. S. FDA announcing the new approval.
This new approval provides another treatment option for patients with newly diagnosed NSCLC with specific mutations. Patients diagnosed with NSCLC should speak with their physician regarding their treatment options as therapy for NSCLC becomes more individually specialized.
Iressa® Active Against Bronchioloalveolar Carcinoma
According to a study published in the Journal of Clinical Oncology, subsets of patients with advanced bronchioloalveolar carcinoma (BAC), a type of non-small cell lung cancer, respond to treatment with Iressa®.
Brochioloalveolar carcinoma is a subtype of NSCLC. In order to evaluate response to Iressa among patients with bronchioloalveolar carcinoma, researchers conducted a phase II clinical trial among 101 previously untreated patients and 35 patients who had previously been treated with chemotherapy. All patients had stage IIIB or stage IV cancer. Patients were treated with 500 mg of Iressa daily.
- Among previously untreated patients, Iressa reduced detectable cancer in 12% of patients and eliminated detectable cancer in 6% of patients.
- Among patients who had previously been treated with chemotherapy, Iressa reduced detectable cancer in 9% of patients. None of the previously treated patients experienced a complete disappearance of detectable cancer following treatment with Iressa.
- Median survival was 13 months for both previously treated and previously untreated patients.
- The most common adverse effects of treatment were rash and diarrhea. Three patients died of interstitial lung disease possibly due to treatment.
- A response to treatment was more common among women, among patients who developed a rash after treatment, and among patients with better functional status.
The researchers conclude that Iressa produces a treatment response in some patients with advanced bronchioloalveolar carcinoma. Responses were observed among both previously treated and previously untreated patients.The researchers note that it’s uncertain whether the results observed in this study are superior to the results that would be obtained with chemotherapy, or whether patients with bronchioloalveolar carcinoma are more likely to respond to Iressa than patients with other types of non-small cell lung cancer. They note, however, that the long-term survival observed among patients in this study was “encouraging.”
- United States Food and Drug Administration. FDA approves targeted therapy for first-line treatment of patients with a type of metastatic lung cancer. Companion test also approved to identify appropriate patients. Available at: . Accessed July 14, 2015.
- West HL, Franklin WA, McCoy J et al. Gefitinib Therapy in Advanced Bronchioloalveolar Carcinoma: Southwest Oncology Group Study S0126. Journal of Clinical Oncology. 2006;24:1807-1813.
- Douillard JY et al. First-line gefitinib in Caucasian EGFR mutation-positive NSCLC patients: a phase-IV, open-label, single-arm study. Br J Cancer 2014 Jan 7; 110, 55-62. doi: 10.1038/bjc.2013.721.
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