CONTINUATION THERAPY: Patients receive vincristine sulfate IV over 1 minute or infused via minibag on day 1, cyclophosphamide IV over 1 hour on days 1-3, etoposide IV over 60-120 minutes on days 21-23, and carboplatin IV over 1 hour on days 21-23. Treatment repeats every 42 days for 2 courses in the absence of disease progression or unacceptable toxicity.