Histologic subtype in NSCLC: does it matter?

Platinum-based doublet chemotherapy remains the cornerstone of therapy in the first-line setting in advanced non-small-cell lung cancer (NSCLC) for patients with good performance status. However, this paradigm has recently been challenged by the results of a study that showed a survival benefit with the addition of bevacizumab to carboplatin and paclitaxel in bevacizumab-eligible patients and by the superior efficacy of gefitinib and erlotinib compared to chemotherapy in epidermal growth factor receptor (EGFR) gene mutation-positive tumors (mainly adenocarcinomas). In addition, histology has been recently recognized as a potential predictive factor in advanced NSCLC patients treated with chemotherapy. Prospective data from a preplanned subgroup analysis of a phase III study and retrospective reviews consistently reported a significant interaction between treatment by histology and response/survival in nonsquamous NSCLCs treated with pemetrexed, compared to squamous cell carcinoma (SCC). Thymidylate synthase, the main target of pemetrexed, was found to be differentially expressed among the histotypes of lung cancer, being lower in adenocarcinoma and higher in SCC and small-cell lung cancer. Thus, the availability of adequate amounts of tissue from biopsies to allow accurate pathologic subclassifications at diagnosis will be critical to help the oncologist select the most appropriate chemotherapy regimen as we move toward an individualized molecularly based approach.