Predicting response to paclitaxel/carboplatin-based therapy in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is a systemic illness. The majority of newly diagnosed patients depend on systemic chemotherapy to improve outcome. Among the new chemotherapeutic agents recently tested, paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) has shown convincing single-agent activity in advanced NSCLC. The two initial phase II studies using paclitaxel alone showed a 1-year survival rate of 40%, comparable to that seen with combination regimens. Paclitaxel/carboplatin is one of several standard regimens for patients with stage IIIB to IV disease. It is as effective as any other new agent/platinum combination studied to date; it is easy to administer and well tolerated. Identification of the molecular and genetic events involved in each step of tumor progression seems to be crucial both to understanding lung cancer and for the development of new pharmacologic compounds that target specific cellular processes affecting growth and proliferation. An innovative strategy is to combine established chemotherapy with these new compounds. Resistance to available chemotherapy drugs is the major obstacle to effective chemotherapy. Genetic abnormalities could play a role in outlining some patterns of chemoresistance. Acquired resistance to paclitaxel can be mediated by several mechanisms, including overexpression of p-glycoprotein, altered expression of beta-tubulin isotypes, intrinsic or acquired mutations in beta-tubulin, and expression of novel genes. Beta-tubulin mutations were recently identified in 33% of 49 NSCLC patients, none of whom had an objective response to paclitaxel treatment. Cisplatin resistance is associated with several molecular alterations, including overexpression of metallothionein and the mRNA level of the excision repair cross-complementing (ERCC1) gene. Early detection of circulating cancer cells in peripheral blood would enable more accurate lung cancer staging. Furthermore, sequential measurements of DNA concentration may be used to monitor the effects of therapy. Serum DNA can be used as a surrogate for detecting genetic abnormalities and as a potential guide for customizing treatment. We analyzed the presence of beta-tubulin mutations in serum DNA from NSCLC patients and from healthy individuals. Beta-tubulin mutations were detected in 42% of the 131 patients and in none of the control group. Several clinical studies are proposed to develop more customized approaches in lung cancer.