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.