Peripheral blood stem cell support for multiple cycles of dose intensive induction therapy is feasible with little risk of tumor contamination in advanced stage neuroblastoma: a report from the Childrens Oncology Group.

BACKGROUND: Poor outcome in Stage 4 neuroblastoma may be improved with increased dose intensity of therapy. We investigated the feasibility of sequential collection and infusion of peripheral blood stem cells (PBSCs) as hematopoietic support for non-myeloablative dose intensive induction chemotherapy given every 21-28 days. METHODS: Twenty-two children with Stage 4 neuroblastoma (>or=1 year of age) received two cycles of high-dose cyclophosphamide (4 g/m(2)), doxorubicin (75 mg/m(2)), and vincristine (2 mg/m(2)) followed by three cycles of interpatient dose escalating carboplatin (Dose Level 0 = 800 mg/m(2); Dose Level 1 = 1,000 mg/m(2)), high-dose cyclophosphamide (4 g/m(2)), and etoposide (600 mg/m(2)). PBSC were harvested following cycle 2, 3, and 4 in Cohort 1 and infused after each subsequent cycle. In Cohort 2, PBSC were harvested after cycle 2 and split into three aliquots for infusion. Dose limiting toxicity (DLT) and ability to administer cycles within 28 days was assessed. RESULTS: Sufficient PBSC (>or=2 x 10(6) CD34 cells/kg per infusion) were collected from 17/21 eligible patients with minimal toxicity and no detectable neuroblastoma cells by immunocytology. Carboplatin at 1000 mg/m(2) resulted in DLT of delayed platelet recovery >28 days in 4/8 patients. Despite de-escalation to 800 mg/m(2), platelet DLT occurred in 4/7 Cohort 1 and 3/7 Cohort 2 patients. CONCLUSION: As defined in this protocol, doses of carboplatin were not tolerable with the PBSC dose administered. However, it was feasible to collect sufficient PBSC from small neuroblastoma patients to use as hematopoietic support with minimal risk of tumor contamination and toxicity.

Haplotyping a quantitative trait with a high-density map in experimental crosses.

BACKGROUND: The ultimate goal of genetic mapping of quantitative trait loci (QTL) is the positional cloning of genes involved in any agriculturally or medically important phenotype. However, only a small portion (< or = 1%) of the QTL detected have been characterized at the molecular level, despite the report of hundreds of thousands of QTL for different traits and populations. METHODS/RESULTS: We develop a statistical model for detecting and characterizing the nucleotide structure and organization of haplotypes that underlie QTL responsible for a quantitative trait in an F2 pedigree. The discovery of such haplotypes by the new model will facilitate the molecular cloning of a QTL. Our model is founded on population genetic properties of genes that are segregating in a pedigree, constructed with the mixture-based maximum likelihood context and implemented with the EM algorithm. The closed forms have been derived to estimate the linkage and linkage disequilibria among different molecular markers, such as single nucleotide polymorphisms, and quantitative genetic effects of haplotypes constructed by non-alleles of these markers. Results from the analysis of a real example in mouse have validated the usefulness and utilization of the model proposed. CONCLUSION: The model is flexible to be extended to model a complex network of genetic regulation that includes the interactions between different haplotypes and between haplotypes and environments.