Subsequently, Park et al. reported the results of CD34+ cell collection in 32 patients with MM using single-dose etoposide (375 mg/m2 for one day) plus G-CSF mobilization, which showed a better safety profile of febrile neutropenia in two (6.3%) patients, without other toxicities such as mucositis, pneumonia, and bacteremia, and without decreased rates of optimal (CD34+ cells of 5 × 106/kg or greater; 71.9%) and adequate (CD34+ cells of 3 × 106/kg or greater; 87.5%) collection. Here, CD34 is linked to susceptibility to pneumonia measurement.