High-dose cytarabine for intensification of early therapy of childhood acute myeloid leukemia: A Pediatric Oncology Group study

In June 1984, the Pediatric Oncology Group (POG) initiated a pilot study (8498) using high-dose cytarabine (HdA; 3 g/m²) for intensification of early therapy in childhood acute myelogenous leukemia (AML) (group I). Remission induction therapy consisted of two courses of daunorubicin, cytarabine (Ara-C), and thioguanine (DAT). Postremission therapy consisted of four sequential courses, each consisting of (1) four doses of HdA (HdA₄ followed by asparaginase (L-Asp), (2) etoposide (VP) plus azacytidine (Az), (3) prednisone, vincristine, methotrexate, and mercaptopurine (POMP), and (4) Ara-C daily for 5 days by continuous infusion. Six doses of intrathecal Ara-C were given for CNS prophylaxis. In December 1986, the protocol was amended (group II) to substitute six doses of HdA (HdA₆) for the second DAT (two + five) induction course; postinduction, a single course of HdA₆ was given instead of four HdA/L-Asp courses, and the remainder of the therapy was unchanged. One hundred forty group I patients and 145 group II patients were assessable. The two groups were similar with regard to clinical prognostic groups. No significant differences were noted in the two groups with regard to remission induction (85% [SE = 2%] in each group), induction deaths (6.5% v 7.0%), or deaths in remission (one in each group). Cerebellar toxicity was reported in three patients in group II (with HdA₆) but none in group I (HdA₄). At present, patients who received HdA₆ (group II) had higher event-free survival than patients in group I (EFS at 3 years, 34% [SE = 11%] v 29% [SE = 4%]), and disease-free survival (DFS at 3 years, 42% [SE = 14%]v34%[SE = 4%]), but the differences were not statistically significant. In both groups, children less than 2 years and those with WBCs less than 100,000/μL had significantly better outcome (EFS of 55% [SE = 10%] and 36% [SE = 5%] at 3 years, respectively) than children ≥ 2 years and those with WBCs ≥ 100,000/μL (EFS of 27% [SE = 5%] and 20% [SE = 9%] at 3 years, respectively.