Association of telomere length of peripheral blood leukocytes with hematopoietic relapse, malignant transformation, and survival in severe aplastic anemia

Abstract

Context: Critically short telomeres produce apoptosis, cell senescence, and chromosomal instability in tissue culture and animal models. Variations in telomere length have been reported in severe aplastic anemia but their clinical significance is unknown.

Objective: To investigate the relationship between telomere length and clinical outcomes in severe aplastic anemia.

Design, setting, and patients: Single institution analysis of 183 patients with severe aplastic anemia who were treated in sequential prospective protocols at the National Institutes of Health from 2000 to 2008. The pretreatment leukocyte age-adjusted telomere length of patients with severe aplastic anemia consecutively enrolled in immunosuppression protocols with antithymocyte globulin plus cyclosporine for correlation with clinical outcomes were analyzed.

Main outcome measures: Hematologic response, relapse, clonal evolution, and survival.

Results: There was no relationship between hematologic response and telomere length with response rates of 56.5% of 46 patients in the first, 54.3% of 46 in the second, 60% of 45 in the third, and 56.5% of 46 in the fourth quartiles. Multivariate analysis demonstrated that telomere length was associated with relapse, clonal evolution, and mortality. Evaluated as a continuous variable, telomere length inversely correlated with the probability of hematologic relapse (hazard ratio [HR], 0.16; 95% confidence interval [CI], 0.03-0.69; P = .01). The probability of clonal evolution was higher in patients in the first quartile (24.5%; 95% CI, 8.7%-37.5%) than in quartiles 2 through 4 (8.4%; 95% CI, 3.2%-13.3%; P = .009), and evolution to monosomy 7 or complex cytogenetics was more common in the first quartile (18.8%; 95% CI, 3.5%-31.6%) [corrected] than in quartiles 2 through 4 (4.5%; 95% CI, 0.5%-8.2%; P = .002) [corrected]. Survival between these 2 groups differed, with 66% (95% CI, 52.9%-82.5%) surviving 6 years in the first quartile compared with 83.8% (95% CI, 77.3%-90.9%) in quartiles 2 through 4 (P = .008).

Conclusion: In a cohort of patients with severe aplastic anemia receiving immunosuppressive therapy, telomere length was unrelated to response but was associated with risk of relapse, clonal evolution, and overall survival.

Figures

Figure 1

Cumulative incidence of relapse according to pre-treatment telomere length. Incidence of relapse per quartile. A greater rate of relapse was observed with each quartile as the telomere length shortened from the fourth to the first quartile.

Figure 2

Cumulative incidence of clonal evolution according to pre-treatment telomere length. (A) Incidence of clonal evolutions in the first quartile (shortest) compared to quartiles 2–4. (B) Incidence of monosomy 7 or complex cytogenetics in the first quartile (shortest) compared to quartiles 2–4.

Figure 3

Overall survival according to pre-treatment telomere length and absolute reticulocyte count (ARC). (A) Overall survival according to pre-treatment telomere length. A superior 6-year survival was observed in those in quartiles 2–4 compared to those in the first (shortest) quartile. (B) Overall survival according to pre-treatment telomere length and ARC. A favorable outcome was observed in patients with both a high ARC and longer telomeres (quartiles 2–4) compared to those with a low ARC and with the shortest telomeres (first quartile). An intermediate group with either a low ARC and longer telomere (quartiles 2–4) or a high ARC and with the shortest telomere length (first quartile) was observed. A high ARC was defined as ≥ 25,000/μL and a low ARC