Systemic approaches for multifocal bronchioloalveolar carcinoma: is there an appropriate target?

Bronchioloalveolar carcinoma (BAC) is a subset of pulmonary adenocarcinoma characterized by distinct and unique pathological, molecular, radiographic, and clinical features. While the incidence of pure BAC is rare, comprising only 1% to 4% of non-small-cell lung cancer (NSCLC), mixed subtypes (including BAC with focal invasion and adenocarcinoma with BAC features) represent as much as 20% of adenocarcinomas--and that figure may be increasing. Despite the longstanding recognition of this entity, there is no established treatment paradigm for patients with multifocal BAC, resulting in competing approaches and treatment controversies. Current options for multifocal BAC include both surgery and systemic therapies. Unfortunately, prospective data on systemic approaches are limited by study design and small patient numbers; there are only seven phase II studies involving four therapies. This article evaluates key characteristics of BAC, including the current understanding of histopathology and tumor biology. In addition, it comprehensively reviews the systemic phase II studies in an attempt to clarify the therapeutic challenges in this disease. It also includes the first proposed treatment paradigm that integrates both EGFR mutational status and the sub-histologies, mucinous and nonmucinous BAC.