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Z.R. Rogers et al.
log-rank test. A Cox proportional hazards model was used to compare EFS by treatment adjusting for co-variates of interest [age, gender, time from initial IST treatment to 2nd treatment, and lymphocytopenia (lymphocyte count <1x109/L)]. Reference groups in this model were: IST treatment, age at second treatment ≥10 years, male gender, lymphocyte count at diagnosis ≥1x109/L. An indicator variable was included in the model for missing lym- phocyte data as these data were not provided for all subjects. The median follow up among all subjects was 62 months. There was 80% power to detect differences of at least 16% difference in pro- portions for 314 and 264 subjects, respectively (two-sided Fishers exact test, alpha=0.05). In terms of precision, the maximum Confidence Interval width of the exact binomial 95%CI for an observed proportion was 0.12 and 0.11, respectively, with n=314 and n=264. R language was used for analysis (R Core Team, 2016, Vienna, Austria; https://www.R-project.org).
Results
Patients' characteristics at diagnosis
A total of 314 pediatric patients treated with IST for SAA were identified by systematic retrospective chart review across 25 NAPAAC institutions. Table 1 summa- rizes baseline demographics of study subjects. Nine patients (0.03%) were 1-2 years of age. Gender was even- ly distributed. The population was racially diverse, reflect- ing the ethnic diversity of North America. A family histo- ry of aplastic anemia, none of whom were first-degree rel- atives, was noted in four patients.
Hepatitis was noted prior to diagnosis in 43 (13.7%) patients, of whom 33 (12.5%) were treated with hATG/cyclosporine (CyA). Laboratory features at diagno- sis are summarized in Table 2. PNH test results were available at diagnosis for 140 patients and a PNH clone
Table 1. Baseline demographics and characteristics.
Total subjects (N)
Male gender (N, %)
Median age in years at diagnosis (Range) Race (N,%)
White*
Black or African American
Asian
Other
Native Hawaiian or Other Pacific Islander
Native American or Alaska Native
Unknown
Study subjects All subjects
314
162 (51.6%) 9.8 (1-20.3)
183 (58.3%)
52 (16.6%)
23 (7.3%)
33 (10.5%)
11 (3.5%)
1 (0.3%)
11 (3.5%)
hATG/CyA
264
141 (53.4%) 9.6 (1-20.3)
157 (59.5%) 42 (15.9%) 19 (7.2%) 24 (9.1%) 11(4.2%) 1 (0.4%) 10 (3.8%)
*Including Hispanic and Latino; hATG: horse anti-thymocyte globulin.; CyA: cyclosporin.
Table 2. Laboratory features at diagnosis.
PNH clone detected, N (%) 140
Median MCV, fL (IQR) 273 MCV > 100fL, N, (%) 273 Median absolute reticulocyte 231
count x109/L (IQR)
Median lymphocyte count/mL (IQR) 260
Lymphocyte count <1000/mL, N (%) 260
All subjects NN
Evaluable
hATG/CyA subjects Value Evaluable
Value
48(44%)
89.1 (83.0-98.8) 51 (21.8%) 20 (10, 33)
1260 (650-1950) 89 (40.3)
55 (39.3%) 109
89.1 (83.1-97.8 ) 234 55 (20.1%) 234 19 (9,33) 190
1210 (600-1890) 221 110 (42.3%) 221
PNH: paroxysmal nocturnal hemoglobinuria; MCV: mean red cell volume; fL: fentoliter; IQ: IQR: interquartile range.
Table 3. Treatment. Treatment
hATG+CyA
hATG+Tacro rATG+CyA or Tacro CTX
Unspecified ATG+CyA
N (%)
264 (84.1%)
15 (4.8%) 15 (4.8%) 19 (6.1%)
1 (0.3%)
Tacro: tacrolimus, CTX: cyclophosphamide; hATG: horse anti-thymocyte globulin; rATG: rabbit anti-thymocyte globulin; CyA: cyclosporine.
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haematologica | 2019; 104(10)