In order to decrease this relapse risk in high-risk patients, the investigators initiated a myeloablative haploidentical HSCT study in January 2009 utilizing Busulfan-based conditioning, post-transplant Cy, and PBSC, instead of BM, as the stem cell source. Outcomes of the 15 patients transplanted to date have been promising with 100% engraftment, low rates of treatment-related mortality, relapse and GVHD, and excellent survival rates. An unexpected outcome of the study was a higher-than-expected rate of BK virus-induced hemorrhagic cystitis (HC) occurring in 7 of 14 evaluable patients. Although there were no deaths attributable to HC, it was associated with significant morbidity in some patients.