Emerging approaches to advanced bronchioloalveolar carcinoma

Bronchioloalveolar carcinoma (BAC) is a subtype of non-small cell lung adenocarcinoma that has distinct epidemiologic, histologic, radiographic, and clinical features. The strict pathologic definition requires an absence of any invasion through the basement membrane into pulmonary parenchyma, but there is a growing consensus based on recent clinical studies that this diagnosis should be considered to be based on the clinical features of diffuse ground-glass opacities with minimal or no extra-thoracic spread and histology demonstrating adenocarcinoma with a lepidic growth pattern characteristic of BAC, even if there is a component of invasive adenocarcinoma. Although unifocal or even potentially oligometastatic disease is appropriately treated with resection, advanced BAC is generally treated with systemic therapy. However, multifocal BAC may be indolent enough to follow asymptomatic patients without any systemic therapy if patients are comfortable with this approach, because the rate of disease progression may be slow enough to warrant no therapy for many months or even years. For patients who have symptoms and/or clear evidence of progression over a short interval, standard chemotherapy is appropriate, but I would consider treatment with the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) erlotinib to be the most appropriate initial therapy. This is based on the well-documented activity of the EGFR TKIs erlotinib and gefitinib, the latter no longer commercially available in advanced BAC. Advanced BAC is now emerging as an area of significant research, and clinical trials are particularly appealing considerations for such patients.

Systemic Therapy of Advanced Bronchioloalveolar Cell Carcinoma: Challenges and Opportunities

Bronchioloalveolar cell carcinoma (BAC) has fascinated physicians with its unique epidemiology, pathology, clinical manifestations, and natural history when compared with other non–small-cell lung cancer (NSCLC) subtypes. However, the relative rarity of pure BAC as defined by the WHO, and the inconsistent definitions used in various series, has limited systematic study of this entity. Retrospective and prospective studies suggest that patients with BAC treated with cytotoxic chemotherapy have a longer median survival than those with other subtypes of NSCLC. However, the widely accepted view that BAC is less chemosensitive than other NSCLCs is not clearly supported by the small body of available literature. Antitumor activity of cytotoxic agents and the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors has been documented in phase II trials but no phase III trials have been conducted in this disease. The observation that profound responses to gefitinib and erlotinib often occurred in NSCLC patients with BAC, and that EGFR tyrosine kinase domain mutations were identified in large part by careful study of such patients, serves as a paradigm for translational research in this disease. The recognition that pure BAC and adenocarcinoma with BAC features behave similarly and as such represent a relatively common entity will facilitate accrual to BAC specific studies. Alternatively, stratification of these histologic subtypes in broader clinical trials in NSCLC is warranted. However, for either strategy to succeed in advancing our understanding of the molecular biology of BAC, it must be accompanied by central pathologic review with detailed classification of such, and of adequate tissue for measurement of known or putative targets of action of the agent under study.

Epidermal growth factor receptor mutations, small-molecule kinase inhibitors, and non-small-cell lung cancer: current knowledge and future directions

PURPOSE

Gefitinib and erlotinib are small molecules that selectively inhibit epidermal growth factor receptor (EGFR) tyrosine kinase activity. When these drugs were introduced into the clinic, the specific targets affected in human tumors were unknown. In April 2004, two groups reported that mutations in the tyrosine kinase domain of EGFR are strongly associated with gefitinib sensitivity in patients with non-small-cell lung cancer (NSCLC). We subsequently extended these findings and showed that such mutations are also associated with sensitivity to erlotinib. Here, we present current knowledge about EGFR mutations in the context of clinical trials involving gefitinib and erlotinib in NSCLC.

DESIGN

This article reviews the rationale for targeting EGFR, the development of gefitinib and erlotinib, the discovery of EGFR mutations, and subsequent studies to define the incidence, spectrum, and functions of EGFR mutations.

RESULTS

The discovery of EGFR mutations promises to alter the ways in which we consider and treat NSCLC.

CONCLUSION

This information can guide practitioners and help them inform their patients about EGFR mutations and their impact on the treatment of NSCLC.

EGFR mutations in non-small-cell lung cancer: analysis of a large series of cases and development of a rapid and sensitive method for diagnostic screening with potential implications on pharmacologic treatment

PURPOSE

It has been reported that EGFR mutations in lung carcinomas make the disease more responsive to treatment with tyrosine kinase inhibitors. We decided to evaluate the prevalence of EGFR mutations in a large series of non-small-cell lung carcinomas (NSCLCs) and to develop a rapid and sensitive screening method. PATIENTS AND METHODS We examined 860 consecutive NSCLC patients for EGFR mutations in exons 18, 19, and 21 using a dual technical approach--direct sequencing of polymerase chain reaction (PCR) products and PCR single-strand conformation polymorphism (SSCP) analysis. Moreover, all lung adenocarcinomas were analyzed for K-ras mutations at codon 12 by allele-specific oligoprobe hybriditations.

RESULTS

There were no EGFR mutations in 454 squamous carcinomas and 31 large cell carcinomas investigated. Thirty-nine mutations were found in the series of 375 adenocarcinomas (10%). Mutations were present in 26% of 86 bronchioloalveolar carcinomas (BACs) and in 6% of 289 conventional lung adenocarcinomas; P = .000002. EGFR mutations and K-ras mutations were mutually exclusive. A multivariable analysis revealed that BAC histotype, being a never smoker, and female sex were independently associated with EGFR mutations (odds ratios: 4.542, 3.632, and 2.895, respectively). The SSCP analysis was accurate and sensitive, allowing identification of mutations that were undetectable (21% of cases) by direct sequencing.

CONCLUSION

Mutations in the EGFR tyrosine kinase domain define a new molecular type of lung carcinoma, more frequent in particular subsets of patients. The SSCP assay is a rapid and reliable method for the detection of EGFR kinase domain mutations in lung cancer.

Gefitinib therapy for non-small cell lung cancer

Gefitinib is a small molecule that specifically inhibits the tyrosine kinase activity of the epidermal growth factor receptor (EGFR) type 1 by interfering with the adenosine triphosphate (ATP) binding site. At doses that maximally inhibit EGFR tyrosine kinase activity chosen for phase II trials, the most common side effects of gefitinib are low-grade rash or diarrhea. An infrequent but serious side effect of gefitinib is interstitial lung disease (ILD). The Iressa dose evaluation for advanced lung cancer phase II trials (IDEAL 1 and IDEAL 2) of single agent gefitinib, 250 or 500 mg orally per day in pretreated patients with non-small cell lung cancer (NSCLC), found about 20% of patients on IDEAL-1 and 10% of patients on IDEAL-2 had major objective responses and improvement of symptoms. The data from the IDEAL trials and the extensive experience from the 21,000 patients treated on the expanded access program, suggests that the patients who have a major objective response probably have a significant survival benefit in addition to palliative benefit. In addition, approximately 40% of patients on the IDEAL trials experienced improvement in symptoms. Gefitinib was approved for third line treatment of NSCLC. Gefitinib is effective, safe, and well-tolerated single-agent therapy in previously treated NSCLC. Although there have been no direct comparisons, the small molecule inhibitors of EGFR gefitinib and erlotinib appear to have similar efficacy. Erlotinib has been shown to produce a survival advantage compared to best supportive care in an unselected group of previously treated patients with NSCLC. Until similar trials are completed comparing gefitinib to best supportive care, there is a similar survival advantage for gefitinib. Nonsmokers, women, and patients with adenocarcinoma, are more likely to have major objective responses than other patients. Bronchioalveolar lung cancer is a subtype of NSCLC that is more likely to respond to gefitinib. Several groups have now reported that most, but not all, tumors experiencing a major objective response to gefitinib have mutations associated with the ATP-binding site of EGFR. It is reasonable to move gefitinib in to second-line therapy for patients who are known to have a tumor that is more likely to respond to gefitinib. Also, I would treat such patients with gefitinib as first-line therapy on an appropriate clinical trial approved by the Institutional Review Board (IRB). Outside of a clinical trial, patients with advanced disease should initially be treated with a combination of doublet chemotherapy. There is strong evidence that there is no benefit to concurrent chemotherapy and gefitinib. Gefitinib should not be given concurrently with cytotoxic chemotherapy as initial treatment for NSCLC. Sequential therapy combining chemotherapy and gefitinib in advanced disease or as adjuvant therapy should only be done in the context of a clinical trial approved by the IRB. There is preclinical evidence suggesting that gefitinib is a radiosensitizer. Early results from trials combining radiation, or chemoradiotherapy with gefitinib have shown that these combinations are without excessive additive toxicity. There is no proven clinical benefit for concurrent Gefitinib and radiation. Gefitinib should only be given with radiation as part of an appropriate clinical trial approved by the IRB.