Intensified Myeloablative Unrelated Cord Blood Transplantation for High-Risk or Advanced Hematological Malignancies: Experience at a Single-Institution in China

Introduction : Unrelated cord blood transplantation (CBT) is one of the most promising curative treatment modalities for hematological malignancies. But the data was limited in China. This retrospective study evaluated the clinical outcomes of intensified myeloablative unrelated CBT for high-risk or advanced hematological malignancies in our single center.

Patients and Methods: From September 2006 to December 2013, Total of 187 high-risk or advanced hematologic malignancies underwent intensified myeloablative unrelated CBT. All CBT patients received a myeloablative conditioning regimen of TBI/Ara-C/CY [total body irradiation (TBI, total 12 Gy, 4 fractions) (d-7, d-6) arabinoside cytarabine (Ara-C) (2.0g/m2 every 12h for 2 days) (d-5, d-4) and cyclophosphamide (CY, 60 mg/kg daily for 2 days) (d-3, d-2)] (age≥14 years or primary induction failure or no remission after relapse), or Fludarabine/BU/CY2 [fludarabine (Flu, 30mg/m2 daily for 4 days) (d-8~ -5), busulfan (0.8mg/kg every 6h for 4 days) (d-7~ -4) and CY (60 mg/kg daily for 2 days) (d-3, d-2)] (For lymphoid malignancies patients with age ＜14 years or prior radiotherapy which would presuppose a high risk of toxicity), or Ara-C/BU/CY2 [ Ara C (2.0g/m2 every 12h for 2 days) (d-9, d-8), (busulfan (0.8mg/kg every 6h for 4 days) (d-7~ -4) and CY (60 mg/kg daily for 2 days) (d-3, d-2)](for myeloid malignancies patients with age < 14 years or prior radiotherapy which would presuppose a high risk of toxicity), and G-CSF was given with 5 ug/kg daily by subcutaneous injection one day prior to Ara-C with 3 days. For GVHD prophylaxis, all patients were given a combination of cyclosporine and short-course mycophenolate mofetil, and no patient received antithymocyte globulin (ATG).

Results: Total of 181 patients (97.3%) achieved neutrophil engraftment and platelet engraftment, and the median number of days was 18 days (range 12~37 days) and 37.5days (range 15~112 days), respectively. Total nucleated-cell dose (≥5.2×10⁷ / kg) and total CD34⁺ cell dose (≥3.8×10⁵ / kg) were the favorable factors predicting for a higher probability of neutrophil engraftment (p =0.012, 0.025). The cumulative incidence of pre-engraftment syndrome (PES) and day-100 grade Ⅱ-Ⅳ acute GVHD was 75.4% (95% CI, 65.2-84.2%) and 28.34% (95% CI, 28.13~28.55%), respectively. The cumulative incidence of grade Ⅱ-Ⅳ acute GVHD 100 days after transplantation was 32.6% (95% CI, 42.3-22.8%)in the PES group and 15.2% (95% CI, 8.3-22.6%) in the non-PES group (р=0.016). Multivariate analysis showed that BU/CY2 based conditioning and without PES were significant risk factors for graft failure [RR=2.34 (95% CI, 1.32- 6.12), p =0.015; RR=2.89 (95% CI, 1.25- 6.82), p =0.009]. The median follow-up time was 27（7~89）months. Transplant-related mortality at 180 days and relapse at 3 years after CBT was 24.9% (24.7~25.2%) and 14.7% (14.6~14.9%). Probabilities of 3-year overall survival (OS) and disease-free survival (DFS) were 61.2% (95% CI, 51.3%- 72.3%) and 58.6% (95% CI, 49.5%- 67.9%), respectively. For pediatric patients, 3-year OS and DFS were 66.2% (95% CI, 56.4%- 75.8%) and 64.8% (95% CI, 54.6%- 74.2%); for adult patients, 3-year OS and DFS were 54.5% (95% CI, 45.8%- 63.7%) and 50.3% (95% CI, 41.5%- 60.1%), respectively.

Conclusions: To the best of our knowledge, this is the largest clinical study of unrelated CBT reported in China. This retrospective study indicates that intensified myeloablative CBT procedures are associated with significant favorable outcomes in survival advantage in high-risk or advanced hematological malignancies.