Etoposide in patients with previously untreated non-small-cell lung cancer: a phase I study

Loss of cytoplasmic CDK1 predicts poor survival in human lung cancer and confers chemotherapeutic resistance

The dismal lethality of lung cancer is due to late stage at diagnosis and inherent therapeutic resistance. The incorporation of targeted therapies has modestly improved clinical outcomes, but the identification of new targets could further improve clinical outcomes by guiding stratification of poor-risk early stage patients and individualizing therapeutic choices. We hypothesized that a sequential, combined microarray approach would be valuable to identify and validate new targets in lung cancer. We profiled gene expression signatures during lung epithelial cell immortalization and transformation, and showed that genes involved in mitosis were progressively enhanced in carcinogenesis. 28 genes were validated by immunoblotting and 4 genes were further evaluated in non-small cell lung cancer tissue microarrays. Although CDK1 was highly expressed in tumor tissues, its loss from the cytoplasm unexpectedly predicted poor survival and conferred resistance to chemotherapy in multiple cell lines, especially microtubule-directed agents. An analysis of expression of CDK1 and CDK1-associated genes in the NCI60 cell line database confirmed the broad association of these genes with chemotherapeutic responsiveness. These results have implications for personalizing lung cancer therapy and highlight the potential of combined approaches for biomarker discovery.

Etoposide dosage and pharmacodynamics

Etoposide is a schedule-dependent cytotoxic drug with high single agent activity in small-cell lung cancer and lymphoma. Despite its clear dose-dependent myelosuppressive activity, dose-dependent evidence of its anti-tumour activity is harder to demonstrate. A number of reports have correlated haematological toxicity with pharmacokinetic and physiological parameters, which explains some of the variability in dynamic effects that exists between patients. Recent reports have also suggested that anti-tumour response may be related to plasma etoposide concentration. In our own studies we have investigated factors that influence the pharmacodynamic effects of etoposide, principally with regard to haematological toxicity, and these studies have highlighted a number of patient groups who are at risk. Impaired renal function causes a reduction in clearance of etoposide, resulting in increased systemic exposure and more profound myelotoxicity. A 30% dose reduction in this group is recommended to normalise the area under the plasma concentration-time curve (AUC). Patients with low serum albumin concentrations (< 35 g/l) also showed significantly worse haematological toxicity, but with no apparent change in total drug pharmacokinetics. There was, however, an increase in the free drug fraction in this group due to decreased protein binding, such that the free drug AUC was similar to that found in patients with renal dysfunction. This would also indicate that a dose reduction of around 30%-40% is required in this patient group. Patients with normal albumin levels but liver enzyme values (aspartate transaminase or gamma-glutamyl transpeptidase) more than 3 times the upper limit of normal also had a less marked but significant increase in neutropenia. In patients with normal organ function, age was the only significant factor in predicting the degree of leukopenia/neutropenia, and increasing age was also associated with decreasing drug clearance and an increase in drug AUC. A small dose reduction and/or careful monitoring is required in this patient group. Further studies are required to elucidate further the relationship between the pharmacokinetics of etoposide and its pharmacodynamics, particularly with regard to anti-tumor activity, and to determine the role of individualised therapy, based on a pharmacokinetic parameter, in reducing the dynamic variability and optimising the use of this drug.

Etoposide: current status and future perspectives in the management of malignant neoplasms

Etoposide has demonstrated highly significant clinical activity against a wide variety of neoplasms, including germ-cell malignancies, small-cell lung cancer, non-Hodgkin's lymphomas, leukemias, Kaposi's sarcoma, neuroblastoma, and soft-tissue sarcomas. It is also one of the important agents in the preparatory regimens given prior to bone marrow and peripheral stem-cell rescue. Despite its high degree of efficacy in a number of malignancies, the optimal dose, schedule, and dosing form remain to be defined. It is possible that continuous or prolonged inhibition of the substrate, i. e., topoisomerase II, may be the key factor for the cytotoxic effects of etoposide. Clinical studies have shown the activity of etoposide to be schedule-dependent, with prolonged dosing, best accomplished by the oral dosing form, offering a therapeutic advantage. This benefit awaits validation by prospective randomized studies, some of which are in progress. Recent clinical investigations have focused on the use of etoposide in combination with (a) cytokines to ameliorate myelosuppression, the dose-limiting toxicity of etoposide; (b) agents such as cyclosporin A and verapamil to alter the p-glycoprotein (mdr1) function; and (c) topoisomerase I inhibitors to modulate the substrate upon which it acts. There is continued interest in the development of etoposide to its maximal clinical dimensions and in the examination of alternative biochemical and mechanistic approaches to further our understanding of this highly active agent.

The concept of dose intensification in the treatment of neoplastic disease

This paper summarizes different theoretical and clinical approaches contributing to the concept of dose intensification. According to this concept, the amount of antineoplastic drug delivered per time predominantly determines the clinical outcome in patients with neoplastic disease. With the availability of recombinant haemopoietic growth factors haematotoxic side effects might be reduced, making this concept more feasible for clinical use. However, more prospective randomized studies, in which dose-intensity is the only treatment variable, are needed to prove that dose intensification will lead to higher survival rates.