Table 6. Children's Oncology Group (COG) Neuroblastoma Low-Risk Group Assignment Schema Used for COG-P9641 and COG-A3961 Studiesa continued...
Chemotherapy is also reserved for patients who are symptomatic, such as from spinal cord compression or, in stage 4S, respiratory compromise secondary to hepatic infiltration. The chemotherapy consists of carboplatin, cyclophosphamide, doxorubicin, and etoposide. The cumulative chemotherapy dose of each agent is kept low to minimize permanent injury (COG-P9641).
The COG-P9641 study was one of the first COG studies to test risk stratification based on consensus-derived factors. In this phase III nonrandomized trial, 915 patients underwent an initial operation to obtain tissue for diagnosis and biology studies and for maximal safe primary tumor resection. Chemotherapy was reserved for patients with, or at risk of, symptomatic disease, with less than 50% tumor resection at diagnosis or with unresectable progressive disease after surgery alone.
Stage 1: Patients with stage 1 disease achieved 5-year EFS of 93% and 5-year OS of 99%.
Stage 2A and 2B: Asymptomatic patients with stage 2A and 2B disease (n = 306) who were observed after initial operation had a 5-year EFS of 87% and OS rate of 96%. EFS was significantly better for patients with stage 2A than for patients with 2B neuroblastoma (92% vs. 85%; P = .0321), but OS did not differ significantly (98% and 96%; P = .2867). The primary study objective (to achieve a 3-year OS of 95% for asymptomatic patients with stage 2A and 2B disease) was met. Patients with stage 2B disease had a lower EFS and OS for those with unfavorable histology (EFS, 72%; OS, 86%) or diploid tumors (EFS, 75%; OS, 84%) or for patients older than 18 months. Outcome for patients with stage 2B, diploid tumors, and unfavorable histology was particularly poor (EFS, 54%; OS, 70%), with no survivors in the few patients with additional 1p loss of heterozygosity and all deaths occurring in children older than 18 months.
Asymptomatic patients at diagnosis who were observed after initial operation: Of the initial 915 patients, 800 were asymptomatic at diagnosis and observed after their initial operations. Within this group, 11% experienced recurrent or progressive disease. Of the 115 patients who received immediate chemotherapy (median, four cycles; range, one to eight), 81% of the patients had a very good partial response or better. After chemotherapy, 10% of the patients had disease recurrence or progression. For patients treated with surgery alone, the 5-year EFS rate was 89% and the overall survival estimate was 97% and for patients treated with surgery and immediate chemotherapy, the 5-year EFS rate was 91% and the overall survival estimate was 98%.
MYCN amplification: The impact of MYCN-amplified tumors was analyzed in stage I disease. For patients with MYCN-nonamplified tumors the 5-year EFS was 93% and the OS was 99% and for MYCN-amplified tumors the 5-year EFS was 70% (P = .0042) and OS was 80% (P < .001).