All patients that received an Haplo-PTCy at the Intensive Hematological Unit, Hospital del Salvador, from 2016 to 2021 were included. As mentioned, all cases belonged to the national HSCT program, and were approved by a national adult HSCT committee following a specific Haplo-HSCT protocol established in 2016. Inclusion criteria were age ≥15 and ≤40 from 2016-2018 and ≤60 years old since 2019, Eastern Cooperative Oncology Group (ECOG) performance status <3, no concomitant active cancer, and adequate organ function. For patients with acute leukemias, complete response before transplantation was mandatory. This study was performed according to the Helsinki declaration and was approved by the institutional ethics committee. Figure 1

Fig. 1.

Overall survival (A), event-free survival (B), GVHD-free, relapse-free survival (C) and non-relapse mortality (D).

The main endpoints were event-free survival (EFS), OS, cumulative incidence of relapse (CIR), non-relapse mortality (NRM) at two years and graft-versus-host disease (GvHD)-free, relapse-free survival (GRFS) at one year after transplantation. Secondary endpoints were incidence of Grade II-IV acute graft-versus-host disease (aGvHD) at Day +100 and chronic GvHD (cGvHD) at two years. OS was calculated from the day of infusion until the last visit or death by any cause. Glucksberg criteria were used for aGvHD [11,12]. Chronic GvHD was graded using the National Institutes of Health (NIH) criteria [13]. NRM was defined as death from any cause other than relapse. EFS was calculated from the day of infusion until the day of relapse, graft failure or death. GRFS was defined as one year post-transplant survival without Grade III-IV aGvHD, systemic therapy required for cGvHD, relapse, or death.

The haploidentical donor was defined based on molecular techniques for HLA-A, HLA-B and HLA-DRB1 loci. Disease stage at the time of transplantation was classified by the Disease Risk Index (DRI) [14]. The hematopoietic cell transplantation-specific comorbidity index (HCT-CI) was used to stratify patients according to pre-transplant comorbidities [15].

Myeloablative conditioning (MAC) was defined as a regimen containing either total body irradiation with a dose greater than 6 Gy, a total dose of oral busulfan greater than 8 mg/kg bodyweight, or a total dose of intravenous busulfan >6.4 mg/kg bodyweight [16].

Cytokine release syndrome (CRS) was defined as post-infusion fever up to Day +6, with no clinical focus nor microbiologic agent identified and classified according to Lee (Supplementary Table 1) [17]. Neutrophil engraftment was defined as the first day of an absolute neutrophil count ≥0.5 × 109/L lasting for three or more consecutive days and platelet engraftment as ≥20.0×109/L for five consecutive days without transfusional support. Graft failure (GF) was defined as either lack of initial engraftment of donor cells (primary graft failure) or loss of donor cells after initial engraftment (secondary graft failure) with donor chimerism ≤5 %. Engraftment syndrome (ES) was defined as the presence of fever, weight gain, skin rash, and/or respiratory distress according to Spitzer classification [18]. Poor graft function (PGF), as frequent dependence on blood and/or platelet transfusions and/or growth factor support with donor chimerism >5 % in the absence of relapse, drugs, or infections [19]. Quality of life was evaluated based on Karnofsky performance scale.

Hematopoietic progenitors were obtained from unmanipulated peripheral blood mobilization. The best donor was selected, prioritizing negative specific anti-HLA antibodies (DSA) and crossmatch: age <40 years, male gender, ABO compatibility and lower parity of female donor. The conditioning protocols are shown in Table 1 [20–23].

Patients were hospitalized in individual isolation units with positive pressure and 4th generation high efficiency particulate air filters and were assisted by a multidisciplinary Intensive Hematology team. According to the institutional protocol, filgrastim 300 mcg/d sc was universally used from Day +5 until absolute neutrophil count (ANC) >1000. Additional filgrastim, erythropoietin and eltrombopag were allowed if sustained or progressive cytopenias due to infections, drug toxicity, PGF or GF were observed.

Acute GvHD prophylaxis was performed with cyclosporine aiming at levels between 250 and 350 ng/mL from Day +5, mycophenolate 1 g every 8 h orally from Day +5 to Day +35 and in vivo T-cell depletion with cyclophosphamide 50 mg/kg bodyweight iv, on Days +3 and +4 [24].

Antibacterial prophylaxis with ciprofloxacin, acyclovir and fluconazole was used. Febrile neutropenia was managed according to the institutional protocol. Acute GvHD was treated according to its severity. Briefly, global Stage I cases were observed or treated with topical or low-dose systemic steroids (equivalent to prednisone 0.5 mg/kg bodyweight/day). Stage II were treated with standard dose steroids (prednisone 1 mg/kg bodyweight/dose). For Stage III-IV aGvHD, high-dose steroids (prednisone 2 mg/kg bodyweight/dose) were used as first line and calcineurin inhibitors were optimized or restarted. If no response was achieved, mycophenolate or methotrexate was used as second-line treatments. Ruxolitinib was not available during the study period.

Discharge was indicated when engraftment, full oral medication and fluid intake >2.5 L/24 h were achieved. Cyclosporine levels were monitored weekly and cytomegalovirus (CMV) by real time polymerase chain reaction (RT-PCR) biweekly until Day +100. CMV reactivation was defined as a viral load exceeding 1000 copies/mL. CMV disease was diagnosed in cases of clinical signs and symptoms. Preemptive treatment with valganciclovir was used as the first choice in cases of CMV reactivation. Ganciclovir was used in CMV disease. Foscarnet was used in case of severe cytopenias or ganciclovir refractoriness.

All epidemiological data and clinical characteristics of the patients were expressed as frequencies with percentages for categorical variables and the mean with range for numeric variables. OS and EFS were estimated using the Kaplan-Meier method. The cumulative incidence of relapse was calculated using relapse as the primary event and death without relapse as a competing event. R software was used for statistical analysis.

Grade 1-2 CRS was seen in 83 % however no Grade 3-4 CRS was observed. Almost all (98 %) patients had mucositis and 61 % needed parenteral nutrition, with a median duration of 11 days (Range: 2-29 days). All patients had at least one FN episode, 56 % with a gastrointestinal focus. Bacteremia was observed in 23 % of the patients, with Staphylococcus epidermidis being the most common agent. Eighteen percent of patients had a probable invasive aspergillosis.

Neutrophil engraftment was achieved in 96 % of patients, (Median: Day +17; Range: 11-25). Platelet engraftment (>20 × 109/L) was achieved in 95 %, (Median: Day +19; Range: 9-84) and platelets >50×109/L (Median: Day +19; Range: 10-175). PGF was observed in 11 (13 %) patients. Eltrombopag was used in 37 %.

Criteria for ES were identified in 21 (26 %) patients; two patients required low-dose vasopressor drugs or non-invasive ventilatory support, both for less than 48 hours. All patients had a good response with low dose steroids. No mortality was observed.

The incidence of Grade II-IV aGvHD and Grade III-IV at 100 days were 29 % and 5 %, respectively. Grade IV was not observed (Table 2). The median onset was on Day +31 (Range: 13-83): most (89 %) had a good response to oral prednisone (0.5-1 mg/kg bodyweight) with only three (4 %) receiving 2 mg/kg bodyweight. Mycophenolate was used as the second line in four patients and methotrexate in one.

The present cohort showed a two-year incidence of cGvHD of 41 % (31/75) with a median time of presentation on Day +187 (Range: 112-562). Nine (12 %) patients developed moderate-to-severe cGvHD requiring systemic treatment. Overall, complete response was observed in 25 (33.3 %), and partial response in 5 (6.7 %) patients with one patient presenting progressive disease. There were two cGvHD -related deaths, one due to refractory pulmonary cGvHD and one with systemic progression due to poor treatment compliance.

Cytomegalovirus (CMV) reactivation was observed in 63 % (50/82) of patients at a median of Day +37 (Range: 15-77). Of these patients, four developed CMV disease. The median viral load for these reactivations was 1595 copies/mL (Range: 39-87,000). Treatment with valganciclovir was effective in 66 % of cases. Four patients required treatment with ganciclovir, and one patient received foscarnet. Three patients (4 %) developed post-transplant lymphoproliferative disorder, with one requiring chemotherapy.

With a median follow-up of 33 months (Range: 1-84), the estimated three-year EFS and OS of the whole cohort were 64.6 % (95 % confidence interval [95 % CI]: 55-76 %) and 68.3 % (95 % CI: 59-79 %), respectively. Patients with neoplastic disease (n = 77), had a three-year CIR of 23 % (95 % CI: 15-33 %). The two-year NRM cumulative incidence was 13.4 % (95 % CI: 12.2-14.8 %). GRFS at one year was 40.2 %.

As a whole, 26 patients died, 16 due to relapse at a median Day +250 (Range: 81-510), eight due to transplant related mortality (three to sepsis before engraftment from Klebsiella pneumoniae carbapenemase-producing bacteria when specific antibiotic therapy was not available, two due to secondary GF, one on Day +53 due to aGvHD and two on Days +273 and +276 due to cGvHD). Two patients died due COVID-19 pneumoniae on Days +97 and +228.