Risk Factors and Outcome of Chronic GVHD: Analysis of 5,660 Patients Undergoing Unrelated Bone Marrow Transplantation through the Japan Marrow Donor Program.

Background: Chronic GVHD (cGVHD) remains the major cause of late morbidity and mortality after allogeneic stem cell transplantation. However, there are limited data available on cGVHD after unrelated BMT (UR-BMT). We retrospectively analyzed the data of 5,660 patients who underwent UR-BMT through the Japan Marrow Donor Program (JMDP) between January 1993 and June 2004.

Methods: Data were collected by the JMDP using a standard report form. Follow-up reports were submitted at 100 days, 1 year, and then annually after transplantation. Overall survival (OS) was estimated by the Kaplan-Meier method and patients surviving beyond day 100 after transplant were analyzed for the development of cGVHD. The log-rank test was used for univariate analysis and time-dependent Cox proportional hazards modeling was used for multivariate analysis. The cumulative incidence of cGVHD and of relapse was calculated using the Gray method considering death without cGVHD and death without relapse as respective competing risks.

Results: The median age of all patients was 28 years and the median follow-up was 433.5 days after transplant. Estimated 5-year OS of all patients and those with hematological malignancies was 47.4% and 45.5%, respectively. A total of 3,974 patients survived beyond day 100 after transplant and their cumulative incidence of cGVHD was 43.2% at day 500 and 44.9% at day 2,000 post-transplant. The cumulative incidence of extensive cGVHD was 28.8% at day 2,000 post-transplant. In multivariate analysis, variables predicting cGVHD were recipient age (p=0.000), donor age (p=0.002), diagnosis of hematological malignancy (HR=1.99, p=0.000), HLA class I mismatch by either serology or DNA typing (HR=1.24, p=0.020), acute GVHD (I: HR=1.50, p=0.000; II: HR=2.07, p=0.000; III and IV: HR=2.25, p=0.000) and no platelet recovery over 50,000/mm³ before day 100 (HR=1.36, P=0.002). There was a significant difference between patients <20 and ≥20 years old (HR=1.27, p=0.000). However, there were no significant differences between any adults grouped by age decade (p=0.894). OS at 5 years in patients surviving >100 days post-transplant was 62.4% without cGVHD, 68.0% with limited cGVHD, and 55.4% with extensive cGVHD (p=0.000). In the patients with hematological malignancies, OS at 5 years was 58.8%, 67.3% and 55.8%, respectively (p=0.000). Cumulative incidence of relapse of hematological malignancies at day 2,000 in patients surviving >100 days post-transplant was 17.6% with limited cGVHD, 18.4% with extensive cGVHD and 27.1% without cGVHD (P=0.000).

Conclusions: This study provides strong evidence of risk factors for developing cGVHD after UR-BMT and suggests that limited cGVHD provides a survival benefit to patients with hematological malignancies by reducing the risk of relapse without increasing the risk of death from cGVHD. There was a significant difference in occurrence of cGVHD between patients <20 and ≥20 years old but no differences comparing any age ≥20 years.