RATIONALE: Drugs used in chemotherapy, such as methotrexate, vinblastine, doxorubicin, and cisplatin, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Giving more than one drug (combination chemotherapy) may kill more tumor cells. Evaluating blood or tissue samples from patients with cancer may help doctors learn more about changes that occur in DNA, identify biomarkers related to cancer, and predict how well patients will respond to combination chemotherapy.