Graft-Versus-Host Disease (GVHD) and Survival Outcomes after HLA-Haploidentical (Haplo) Bone Marrow Transplant (BMT) Compare Favorably with Matched Related Donor (MRD), and Matched Unrelated Donor (MUD) BMT Utilizing High-Dose Posttransplantation Cyclophosphamide (PTCy)

Background: High-dose PTCy has been shown to effectively reduce acute (a) and chronic (c) GVHD after MRD and MUD BMT and to enable the safe implementation of haplo BMT. However, GVHD-related risk factors and survival outcomes, the impact of donor type, and novel composite endpoints, such as cGVHD-free relapse-free survival (cGFRFS), have not been fully characterized in BMT with PTCy.

Methods: We retrospectively analyzed 582 consecutive adult pts with advanced or poor-risk hematologic malignancies who received allogeneic BMT with PTCy at Johns Hopkins from 2002-2012. All pts received a T-cell replete bone marrow graft and PTCy (50 mg/kg/d IV) on D+3 and +4. Platforms consisted of: 1) myeloablative conditioning (MAC) with Busulfan/Fludarabine or Busulfan/Cy followed by MRD (n = 193; 33%) or MUD (n=119; 20%) allografting and PTCy as sole GVHD prophylaxis; or 2) nonmyeloablative (NMA) conditioning with Fludarabine/Cy/TBI followed by related haplo (n = 270; 46%) allografting and PTCy, mycophenolate mofetil D5-35, and tacrolimus D5-180.

Results: The median follow up was 4 (range 0.3-11.4) years (y). The median pt age at time of BMT was 49 (range 18-66) in the MAC cohort and 54 (range 18-73) in the NMA cohort. On competing risk analysis, the D200 probability of grade II-IV aGVHD was 27% after haplo, 37% after MRD, and 50% after MUD BMT, and grade III-IV aGVHD was 4%, 11%, and 14% respectively. The 3-y probability of cGVHD was 12% after haplo, 8% after MRD, and 19% after MUD BMT. On multivariate analysis adjusted for age and original disease risk index (DRI), MRD and MUD BMT were associated with a statistically significantly higher risk of grade II-IV and grade III-IV aGVHD compared to haplo BMT (each p ≤ 0.001). Compared to haplo BMT, MUD, but not MRD, BMT was also associated with a significantly higher risk of cGVHD (p = 0.009). On multivariate analysis, female into male allografting was independently associated with a higher risk of cGVHD (p = 0.007), whereas age and CMV serostatus of the pt and donor were not statistically significantly associated with risks of acute or chronic GVHD. Pts with grade II-IV aGVHD or cGVHD had a lower probability of relapse, but a higher probability of nonrelapse mortality (NRM) at 3 y compared to pts without GVHD. Among pts with GVHD, an HCT-CI score ≥ 5 was associated with significantly inferior overall survival compared to lower HCT-CI scores. Although MAC matched BMT was associated with less relapse risk than NMA haplo BMT, the 3-y probabilities of NRM, DFS, and overall survival were comparable between the transplant platforms (Table). On multivariate analysis adjusted for pt age and DRI, there were no statistically significant differences in DFS, OS, or cGFRFS in MAC related or unrelated BMT compared to NMA haplo BMT.

Conclusions: High-dose PTCy safely modulates acute and chronic GVHD across multiple BMT platforms. The apparently lower risk of aGVHD after NMA haplo BMT with PTCy likely reflects the reduced conditioning intensity and longer duration of immunosuppression utilized. Despite the limitations inherent to a retrospective analysis, these data suggest that key outcomes after BMT with PTCy are comparable across donor types and conditioning intensities. Notably, in all these settings, 3-y estimates of cGFRFS appeared to approach those of DFS. Thus, PTCy may minimize the late morbidity and mortality of cGVHD and allow earlier implementation of novel posttransplantation strategies for relapse prevention.

* p = NS for all comparisons to haplo BMT on multivariate analysis