A Randomized Trial of Induction Therapy (Daunorubicin, Vincristine, Prednisone versus Daunorubicin, Vincristine, Prednisone, Cytarabine and 6-Thioguanine) in Adult Acute Lymphoblastic Leukemia with Long-term Follow-up: An Eastern Cooperative Oncology Group Study (E3486)