A phase II study of oral etoposide in elderly patients with small cell lung cancer

Small-cell lung cancer: an overview of issues in therapy

As one of the few chemo- and radiosensitive neoplasms among the common epithelial solid tumors of adults, small-cell lung cancer has long tantalized clinical investigators. Although for the last 15-20 years therapy has yielded high remission rates, including substantial complete remission rates, results have not improved very much over nearly two decades of intensive therapeutic research, and long-term disease-free survival remains an elusive goal for the large majority of patients. At this point the number of promising untested hypotheses in therapy is quite small, and major advances will probably have to await either the serendipitous discovery of much more active drugs than we now possess, or else the purposeful development of new approaches based on insights into the nature of the transformed state and the biology of SCLC itself.

Treatment of the elderly patient with small-cell lung cancer

The population of the United States is gradually aging. Within a generation, over 20 percent of the population will be > 65 years of age. Since cancer is a disease of older persons, the incidence of malignancies of all types is expected to increase during the coming decades. In general, since older patients appear to tolerate chemotherapy less well than their younger counterparts, strategies that lessen toxicity and yet maintain efficacy are desperately needed. Recently, the use of single-agent oral etoposide has been shown to be an effective palliative therapy for older patients with small-cell lung cancer. Future studies will need to focus on the unique requirements of older patients in order to improve therapy in these individuals.

Oral etoposide in oncology: an evolving role

Etoposide has been in clinical trials for over 2 decades. From the inception of these investigations, both the oral and intravenous routes have been employed. The oral route has been shown to be convenient, safe, and effective in the trials of diseases such as small cell lung cancer and lymphomas. A recent resurgence of interest has surfaced with its oral application in the elderly and in protracted dosing schedules. Investigations are now under way assessing the relative value of the protracted oral dosing schema in a variety of diseases.

Teniposide as single drug therapy for elderly patients affected by small cell lung cancer

From January 1987 to December 1990, 26/105 previously untreated patients affected by small cell lung cancer (SCLC), not suitable for intensive SCLC treatment since 19 of them were older than 70 years and 7 suffered from severe chronic diseases, received induction therapy consisting of teniposide alone, 60 mg/m2 on days 1-5, every 3 weeks until disease progression. After a minimum of two courses, 24 patients were evaluable for response: 13 with limited disease (LD) and 11 with extensive disease (ED) (2 patients were unevaluable: 1 early death and 1 protocol violation). Response rate, by disease stage, was: in the 13 LD, 1 complete response (CR), 8 partial responses (PR), 2 minor responses and 2 failures; in the 11 ED, 1 CR, 4 PR and 6 failures. The overall response rate was 58% (14/24) (95% confidence limits = 38-78%), comprising 8% CR and 50% PR. Median duration of response was 7 months (range 2-32). Median overall duration of survival was 9 months (range 1.5-36+). Toxicity was haematological WHO grade III in 13% of courses delivered, whereas no further important side-effects were recorded, excluding alopecia, which was common. Teniposide used alone appeared a safe and effective palliative treatment for poor-risk patients; the major limitation was the low CR rate.

Current status of etoposide in the management of small cell lung cancer

Etoposide is a schedule-dependent drug with excellent activity against small cell lung cancer (SCLC). Single-agent etoposide achieves overall response rates ranging from 15% to 84%, depending on the schedule of drug administration and the characteristics of the treated population. The route of etoposide administration (intravenous versus oral) has little impact on response rate, provided appropriate dose adjustments are made for oral therapy. In combination with other active agents, etoposide has proven particularly effective in the management of SCLC. Etoposide can be substituted for doxorubicin or vincristine in the cyclophosphamide, doxorubicin, and vincristine (CAV) regimen without loss of efficacy. The etoposide and cisplatin (EP) combination is thought to be synergistic and has proven to be an effective salvage regimen for CAV failures. A regimen that alternates CAV and EP has been found by some investigators to be modestly more effective against SCLC than CAV alone; however, EP alone may be as useful as an alternating regimen. Most studies to date have demonstrated that EP induction is at least as effective as any other standard induction regimen. However, EP has the potential advantage of being more easily integrated with thoracic radiation therapy (RT). This is particularly important in limited-disease patients: two recent pilot studies employing EP induction with hyperfractionated thoracic RT yielded 2-year survival rates of greater than 50%. These promising results are being evaluated further in an ongoing Phase III trial in the United States. The available data indicate that etoposide is one of the most active agents against SCLC and therefore should be included as a component of induction therapy in all patients. New schedules of etoposide administration warrant further study.

The pharmacology of intravenous and oral etoposide

The epipodophyllotoxin derivative etoposide (VP-16) has been in widespread use both alone and in combination chemotherapy for the past decade. It has phase-specific cytotoxicity that acts in the last S and G2 phases of the cell cycle. Although its mode of action is not certain, it appears to act by causing breaks in DNA by interaction with DNA-topoisomerase II or by the formation of free radicals. Most studies show biexponential decay after the intravenous (IV) administration of etoposide. Approximately 30% to 70% of administered etoposide is excreted, with approximately 45% present in the urine. Etoposide is available in oral and IV preparations. It is highly schedule-dependent, with once-daily doses (e.g., for 5 to 8 days every 21 days) giving results superior to intermittent administration. The bioavailability of oral etoposide is approximately 50%, but its absorption is not linear with increasing dose (e.g., greater than 200 mg/d, bioavailability decreases). Factors influencing the bioavailability of oral etoposide include patient status, concurrent medications, hepatic and renal function, and nausea and vomiting. In numerous clinical trials, etoposide has demonstrated excellent activity against a range of tumors, including small cell lung cancer (SCLC), malignant lymphomas, gestational trophoblastic tumors, Ewing's and soft tissue sarcomas, and germ cell tumors, with more modest activity in other tumors (e.g., non-SCLC). Although few comparative studies have been carried out, available data suggest that oral etoposide administered daily during 5 to 8 days is similar to the IV preparation in range of activity. In a study of 53 elderly patients with SCLC treated with etoposide (200 mg/d for five times), there was a response rate of 79% and a median survival of 9.5 months. These results were similar to those achieved with more intensive IV regimens. Several studies of chronic oral etoposide (50 mg/m2/d for 21 times) have been reported recently. Responses were observed in SCLC and germ cell tumors among patients who had relapsed after standard etoposide-containing regimens. These data suggest that etoposide may be a "new" drug when given in this schedule. The high response rates with oral etoposide suggest that oral administration may be substituted for IV administration. This substitution may allow for greater flexibility in chemotherapeutic administration, less hospitalization, and more acceptable toxicity.

A feasibility study of testing new drugs for small-cell lung cancer in patients with a poor performance status

Testing of new drugs in small-cell lung cancer is definitely necessary for the development of agents that might be effective against this tumor. However, testing such drugs in previously untreated patients with a good performance status (PS) may give rise to ethical problems. When previously treated patients are used in testing, potentially effective agents could well elude discovery. Patients who are not eligible for "standard" combination chemotherapy, e.g. untreated patients with a poor PS, may be suitable for testing of new drugs. To evaluate the potential usefulness of such patients in the testing of new agents, we evaluated an effective drug (etoposide) at a relatively nontoxic dose in a group of 14 patients with a PS of 4 (WHO). Oral etoposide resulted in a response in only 3 cases, whereas 5 subjects died of therapy-related toxicity. We conclude that previously untreated patients with a poor PS are not suitable candidates for the testing of new drugs.