Stable Pulmonary Function after Haploidentical Stem Cell Transplantation with Post-Transplant Cyclophosphamide: A Single Center Experience

Background: Pre- and post-transplant pulmonary function tests (PFT) have been previously analyzed in patients who underwent allogeneic hematopoietic stem cell transplantation (HSCT). A deterioration in pulmonary function could be observed in this setting and accounts for higher morbidity and mortality. Haploidentical allogeneic stem cell transplantation (HAPLO) with post-transplant cyclophosphamide (PTCY) is increasingly used. Limited data exists on evaluation of PFT after HAPLO and the number of patients who underwent HAPLO in previously published studies is negligible. We report the evolution of PFT as well as pre-transplant characteristics and outcomes after HAPLO in the adult setting.

Methods: We retrospectively analyzed 80 HAPLO performed in a single center between 2013 and 2019. All patients with available pre- and post-transplant PFT results were included in the study. The Friedman test was used for comparing PFT at baseline, 100 days and 1 year after HAPLO.

Results: The median follow up was 32 (range: 12-74) months. CMV serology was positive in 45% and 65% of patients were male. The median age was 58 (range: 16-73) years. The proportion of surviving patients with available PFT at 3 months and 1 year were 86% and 68%, respectively. Diagnosis was acute myeloid leukemia in 51% and disease risk index was intermediate-low in 75% of the cases. Disease status before HAPLO was complete remission in 61%. Graft source was peripheral blood stem cells in 91% of the cases. Conditioning regimen was reduced intensity in 40% and the most frequent chemotherapy regimen was thiotepa, busulfan and fludarabine. Graft-versus- host disease (GvHD) prophylaxis consisted of Cyclosporine A (CsA) and mycophenolate mofetil in all but one patient who received methotrexate and CsA. All patients received PTCY, 64 (80%) at days 3 and 5 after HAPLO, 7 (9%) at days 3 and 4, and 9 (11%) at day 3 only. Seventy-three (91%) patients received anti-thymocyte globulin.

In total, 24% of the patients had previously smoked, 8% had type 2 diabetes, and 23% suffered from hypertension. Three patients had a lung infection at baseline, of which one was bacterial and two were possibly aspergillosis. At screening for HAPLO, five (6%) patients had restrictive lung disease, nine (11%) met the criteria for obstructive lung disease, and diffusing capacity for carbon monoxide (DLCO) corrected for hemoglobin was impaired in 74% of the patients. The median forced expiratory volume in the first second (FEV1) was 100 (range: 58-146) before HAPLO, 93 (range: 42-10) at 100 days after HAPLO and 99 (range: 32-144) at 1 year. The median forced vital capacity (FVC) was 106 (range: 57-153), 98 (range: 44-148) and 106 (range: 31-153) at pre HSCT, 100 days and 1 year after HAPLO, respectively. FEV1 and FVC were significantly different over time during the 1 year follow up (p=0.01 and p=0.001, respectively). The median FEV1/FVC was 80 (range 51-105) before HAPLO, 77 (range: 54-103) after 3 months, and 75 (range: 43-100) after 1 year. FEV1/FVC, residual volume, and total lung capacity (TLC) remained stable from baseline to 1 year (p=0.27, p=0.84 and p=0.21, respectively). In contrast, DLCO remained impaired during the follow-up period (p<0.001). The median DLCO was 72 (range: 39-105), 64 (range: 16-105) and 66 (range: 26-104) at baseline, 3 months and 1 year after HAPLO.

Twenty-nine patients had an infectious respiratory complication during the follow-up period. Of these, 19 were bacterial, three were viral, two were fungal and five had no microbial documentation. During the 1-year follow-up period, four patients met the criteria for bronchiolitis obliterans syndrome and two for interstitial lung disease. Of these, only one had died at last follow-up.

The cumulative incidence of grade II-IV acute GvHD was 21% (95% CI 14-33%). At 1 year, the cumulative incidence of chronic GvHD was 26% (95% CI 18-39%). Non-relapse mortality was 9% (95% CI 4-18%) at 100 days and 14% (95% CI 8-24%) at 1 year. Relapse incidence was 3% (95% CI 1-10%) and 14% (95% CI 8-24%) at 100 days and 1 year, respectively. Overall survival was 73% (95% CI 62-82%). In all, 22 patients died. Cause of death was relapse of hematological disease in 7 (35%), infection in 7 (35%), GvHD in 2 (9%), multi organ failure in 4 (20%) and other causes in 2.

Conclusion: We observed a significantly impaired DLCO at baseline, which remained impaired at 3 months and 1 year after HAPLO, but with a substantial stable pulmonary function at 1 year.