BACKGROUND: The use of high-dose chemotherapy (HDC) and autologous hematopoietic stem cell transplant (HSCT) has been used in certain pediatric patients with brain tumours to delay/spare radiotherapy. We aimed to study factors predicting a successful stem cell collection (SCC) and correlate stem cell dose infused with HSCT outcomes. METHODS: A retrospective chart review was undertaken for pediatric patients with brain tumours treated at our centre with HDC/HSCT between 2004-2016. RESULTS: Fifty-five patients were identified (32 male) with median age of 6.3 years at time of SCC (range 0.4-18.7). Patients' diagnoses were medulloblastoma (62%), ATRT (20%), and PNET (18%). Most patients (82%) underwent a single/1-day SCC, while the remaining required 2 SCC procedures. Peripheral blood stem cells were the source in most collections (95%). Successful SCC (CD34 collected greater-than-or-equal-to 2 x10^6/kg/transplant) and ideal SCC (greater-than-or-equal-to 5 x10^6/kg/transplant) was achieved in 85% and 45% of patients, respectively. Use of mobilizing chemotherapy with G-CSF was the only factor associated with achieving an ideal collection, while gender, age, stem cell source, and pre-apheresis peripheral blood CD34 count were not significant. Higher CD34/kg infused was associated with faster neutrophil engraftment in the first 3 courses of HDC/HSCT and platelet engraftment in the first course. CONCLUSIONS: The majority of SCC for autologous HSCT can be successfully completed with a single apheresis session. Mobilization with both chemotherapy and G-CSF yields higher CD34 compared to G-CSF alone. Higher dose of CD34/kg infused was associated with faster neutrophil and to a more limited scale platelet recovery post-HSCT.

Stress caused by early weed competition is known to delay the rate of maize development which may result in a decrease in kernel number. Kernel number in maize is correlated negatively with the length of the anthesis-silking interval (ASI). A short ASI has been identified as an easily measured, visual trait which may identify enhanced drought tolerance in maize. Field studies were conducted to test whether: (1) delaying weed control would result in a lengthening of ASI in both a drought tolerant and non-drought tolerant maize hybrid and (2) the presence of drought tolerance genetics comes at a physiological cost, resulting in a greater yield reduction under weedy conditions. In this study, the response of a drought tolerant hybrid with its non-drought tolerant near-isoline was compared to seven different timings of weed control using wheat as a surrogate competitor. Results confirmed that there was no treatment by hybrid interaction at any site–yr for any of the parameters evaluated. Delaying weed control reduced plant height, leaf tip number, shifted and reduced biomass accumulation, kernel number and grain yield and lengthened ASI for both hybrids. Although yield losses occurred with the delay in weed control timing, no yield differences were observed between hybrids suggesting that there was no additional physiological cost associated with the drought tolerant traits. The drought tolerant hybrid, however, was found to have a shorter ASI, lower kernel number and higher kernel wt compared to the non-drought tolerant hybrid. This study confirmed that delaying weed control can influence the length of ASI, which is an important drought tolerant trait. The lengthening of ASI by early weed competition resulted in a rate of yield loss of 0.13 T ha−1 growing degree days (GDD)−1 when averaged across both hybrids and all treatments.