Chronic oral etoposide. Etoposide is an important drug that has been recently incorporated with other agents in the curative treatment of patients with advanced neoplasms, including germ cell tumors, non-Hodgkin's lymphomas (NHL), and small cell lung cancer (SCLC). Etoposide demonstrates remarkable schedule dependency. A randomized comparison has shown an impressive survival difference for patients with extensive SCLC receiving a 5-day course versus those receiving a 1-day course. Because of these and previous clinical and laboratory data, etoposide is now given intravenously or orally in a 3-day to 5-day schedule. It is generally accepted that approximately 50% of the orally administered drug is absorbed. The authors have initiated several etoposide studies using an extended administration schedule, believing that a prolonged schedule may be superior to the standard 3-day to 5-day schedule. This was initially tested in a Phase I study. Results showed that etoposide (50 mg/m2/d) given over 21 days was feasible and was associated with only moderate toxicity. Several Phase II studies have been completed or are nearing completion, including studies in patients with SCLC, NHL, germ cell tumors, soft tissue sarcoma, renal carcinoma, and ovarian carcinoma. Responses have been seen in all of these groups, particularly in patients with SCLC, lymphoma, and germ cell tumors. In these groups we saw responses in patients who were clearly resistant to etoposide plus cisplatin given in a standard schedule or in some patients who were resistant to high-dose etoposide with bone marrow transplantation. Investigators at Indiana University Medical Center who studied oral etoposide in a similar fashion in patients with advanced germ cell tumors and SCLC achieved results similar to those reported here. The authors have initiated a number of combination chemotherapy programs using the chronic oral form of etoposide. These include patients with SCLC, non-small cell lung cancer, and elderly patients with high-grade and intermediate forms of NHL. In addition, chronic intravenous oral etoposide is being used in salvage approaches for patients with acute myelocytic leukemia and recurrent resistant intermediate-grade and high-grade NHL. Preliminary pharmacokinetic data suggest that a 50-mg/m2 oral dose is highly bioavailable (91% to 96%). Therefore, during a prolonged oral course at 50 mg/m2, many patients maintain a minimum plasma concentration of 1 microgram/ml. Further studies of multiple dose or continuous infusion etoposide to maintain a potentially critical plasma level are in progress. Etoposide administered in this way could represent a "new" drug because many of its features are different, and its activity spectrum may be broader. 