Cyclophosphamide Combined with Prednisone for Cyclosporine-Refractory/Relapsed Large Granular Lymphocyte Leukemia-Associated Pure Red Cell Aplasia

Background Large granular lymphocyte leukemia (LGLL) is a common cause of secondary pure red cell aplasia (PRCA)^[1]. Considering the cytotoxicities of cyclophosphamide (CTX) and methotrexate (MTX), cyclosporine (CsA) is proposed for LGLL-associated PRCA. Due to the rarity of LGLL-associated PRCA, few studies of subsequent therapy for patients failed to CsA have been reported ^[2-5]. Here we retrospectively analyzed the outcomes of 60 patients with LGLL-associated PRCA treated by CsA, which be registered in the China Eastern Cooperation Group for Anemia (CECGA), and reported the results of CTX combined with prednisone (CP) regimen for CsA-refractory/relapsed cases.

Methods and results From January 2016 to May 2022, 60 patients with LGLL-associated PRCA were enrolled in CECGA databse. CsA was administered at a dose of 3~5mg/kg/day with a minimum concentration of 150~200ng/ml. CTX was initiated at a daily dose of 100mg, maintained to response. CTX was discontinued when lymphocyte percentage was lower than 50% of normal level or granulocyte count was less than 0.5×10⁹/L. Prednisone was initiated at a dose of 0.5~1mg/kg/day and gradually typered to discontinuation after four weeks.

Clinical characteristics were describled in Table 1. Treated by CsA, 12 (20%) patients with LGLL-associated PRCA achieved complete response (CR), 14 patients (23%) achieved partial response (PR). STAT3 mutation was detected in 11 cases, and only one harbored STAT5b mutation. The response rate of CsA in patients with STAT3 mutation or not was similar [36% (4/11) vs 45% (19/42), P=0.852]. The patient with STAT5b mutation was resistant to CsA.

Among 21 patients who failed to CsA therapy, 16 cases were refractory to CsA and 5cases relapsed. Treated by CP regimen, they achieved better response [(86% (18/21) vs 43% (9/21), P=0.001)] in the shorter interval [(2.83±0.42) months vs (8.90 ± 0.55) months, P=0.0003)] than by CsA initially (Figure 1).

Deep sequencing of rearranged T-cell receptor (TCR) Vβ complementarity-determiningregion3(CDR3) regions by next-generation sequencing (NGS) was conducted in 29 patients. The predominant V-gene of LGLL clonotypes belonged to the TRBV06 family gene rearrangement was detected in 7 patients. The response rate of CsA in patients with TRBV06 family gene rearrangement was markedly lower than in them without it [14% (1/7) vs 64% (14/22), P=0.035]. Binary-Logistic regression model showed TRBV06 family gene rearrangement was inversely related to response to CsA (P=0.032, OR=17.245)

Discussion/Conclusions Our results indicated that the response rate of CsA in patients with STAT3 mutation or not was similar. Deep sequencing analyses of residuals LGLL clones reveals that CTX could eradicate LGLL clones, providing durable response, low relapse rate, whereas CsA treatment is associated with the persistence of leukemic clones, and high frequency of relapse^{[4, 5]}. CP regimen was effective for patients who failed to CsA, especially whom with TRBV06 rearrangement.

Reference 1. Means RT Jr. Pure red cell aplasia. Blood, 2016, 128(21): 2504~2509.

2. Fujishima N, Sawada K, Hirokawa M, et al. Longterm responses and outcomes following immunosuppressive therapy in large granular lymphocyte leukemia-associated pure red cell aplasia: a Nationwide Cohort Study in Japan for the PRCA Collaborative Study Group. Haematologica, 2008, 93(10): 1555~1559.

3. Balasubramanian SK, Sadaps M, Thota S, et al. Rational management approach to pure red cell aplasia. Haematologica, 2018, 103(2): 221~230.

4. Rajala HLM, Olson T, Clemente MJ, et al. The analysis of clonal diversity and therapy responses using STAT3 mutations as a molecular marker in large granular lymphocytic leukemia. Haematologica, 2015, 100: 91~99.

5. Loughran TP, Zickl L, Olson TL, et al. Immunosuppressive therapy of LGL leukemia: prospective multicenter phase II study by the Eastern Cooperative Oncology Group (E5998). Leukemia, 2015, 29(4): 886~894.

No relevant conflicts of interest to declare.