High CD34 cell doses do not worsen regimen-related toxicity or early mortality after autologous blood stem cell transplantation for breast cancer

Background Some transplant-related complications, such as the engraftment syndrome, are thought to be mediated by cytokines released during expansion of hematopoietic progenitors at the time of neutrophil recovery. Since there is an inverse correlation between CD34 + cell dose and time to neutrophil recovery, we sought to determine if peritransplant toxicity and early mor tality were adversely affected by high CD34 + cell doses. Methods The study group included 186 women with breast cancer who received high-dose cyclophosphamide, carmustine, thiotepa and an autologous PBSC transplant. The median CD34 + cell dose was 5.9 × 10 6 /kg (1.0–154.7 × 10 6 /kg). Patients were categorized by CD34 + cell dose (1.0–3.5, 3.6–5.9, 6.0–19.9, and 20.0–154.7 × 10 6 /kg) for assessment of outcomes. Results Grades 2–4 mucositis occurred in 49%, cardiac toxicity in 7%, pulmonary toxicity in 5%, cystitis in 4%, diarrhea in 3%, renal toxicity in 1%, and central nervous system toxicity in 1%, A Grade 2–4 regimen-related toxi city occurred in 109 patients (59%) and Grade 3–4 in eight patients (4%). Overall survival was 100% at Day 30, 96% at Day 90, and 89% at 1 year. Treatment-related mortality was 3.8%. In multivariate analyses that included prior chemotherapy, disease status, visceral metastases, prior chest radiation and age, CD34 + cell dose group was not an independent risk fac tor for Grade 2–4 mucositis, Grade 2–4 maximum toxicity, Grade ≥3 cumulative toxicity, 90 day survival or 1 year survival. Discussion Ne conclude that CD34 + cell doses >20 × 10 6 /kg do not affect transplant outcome in a negative or positive fashion.