Activity of cladribine combined with cyclophosphamide in frontline therapy for chronic lymphocytic leukemia with 17p13.1/TP53 deletion

Report From the Polish Adult Leukemia Group


  • The following individuals contributed to this article, Bogdan Kaluzewski, MD, PhD and Maria Constantinou, PhD (Department of Medical Genetics, Medical University of Lodz, Lodz, Poland); Barbara Pienkowska-Grela, PhD (Department of Medical Genetics, Institute of Oncology, Warsaw, Poland); Dorota Koczkodaj, PhD (Department of Medical Genetics, Medical University of Lublin, Lublin, Poland); Malgorzata Kowal, MD, PhD (Department of Hematology, Medical University of Lublin, Lublin, Poland); Bernadetta Ceglarek, MD, PhD (Department of Internal Medicine and Hematology, Institute of Hematology and Transfusion Medicine, Warsaw, Poland); and Ilona Seferynska, MD, PhD (Department of Hematology, Institute of Hematology and Transfusion Medicine, Warsaw, Poland).



The 17p13.1 deletion that causes loss of the p53-encoding TP53 gene is the most powerful predictor of a poor response to conventional therapy and shortened survival in patients with chronic lymphocytic leukemia (CLL). The results of this study have demonstrated that the cladribine and cyclophosphamide regimen may improve treatment results in this poor-risk patient population.


In this study, the authors retrospectively analyzed the efficacy and toxicity of 2-CdA with cyclophosphamide combination (the CC regimen) in 20 patients with previously untreated B-cell CLL who had 17p13.1 deletion reported to the Polish Adult Leukemia Group (PALG) registry. The CC regimen consisted of 2-CdA at a dose of 0.12 mg/kg and cyclophosphamide at a dose of 250 mg/m2 given intravenously for 3 consecutive days. The CC cycles were repeated at 28-day intervals for up to 6 cycles.


Overall, 16 of 20 patients (80%) responded to CC therapy, including 10 patients (50%) who obtained a complete response and 6 patients (30%) who obtained a partial response. The median progression-free survival reached 23 months (95% confidence interval, 5-41 months). The overall survival probability at 2 years was 52.5% (95% confidence interval, 26%-79%). Treatment toxicity generally was acceptable. Infections were the most common grade 3/4 complications and occurred in 6 patients (30%).


In this retrospective analysis, the results demonstrated that the CC regimen produced a relatively high response rate in patients with previously untreated CLL who had 17p13.1/TP53 deletion, although the response duration and survival were not satisfactory. It is possible that a combination of the CC regimen with p53-independent agents may improve treatment results in this poor-risk patient population. Cancer 2009. © 2008 American Cancer Society.

Despite the generally long-lasting course of chronic lymphocytic leukemia (CLL), in a proportion of patients, the disease progresses rapidly with drug resistance and a poor outcome. In recent years, novel molecular prognostic factors in CLL were identified, including immunoglobulin heavy-chain variable region (IgVH) mutational status, CD38 and ZAP-70 expression, and cytogenetic abnormalities.1 It is noteworthy that the 17p13.1 deletion is the most powerful predictor of a poor prognosis in patients with CLL of all biologic factors that have been identified to date.2 The negative impact of 17p13.1 deletion is attributed to the loss of the TP53 gene encoding for the p53 protein.2, 3 The deletion of 1 TP53 allele frequently is accompanied by TP53 mutations in the other allele, resulting in the total disruption of the p53 pathway.4 The 17p13.1 deletion is detected by interphase fluorescence in situ hybridization (FISH) in approximately 5% of patients with B-cell CLL (B-CLL) on frontline therapy and in much a higher proportion of patients with refractory/relapsing disease.2, 4

The purine nucleoside analogues (PNA) fludarabine (FA) and cladribine (2-chlorodeoxyadenosine [2-CdA]) induce more durable responses than alkylator-based therapies and play a central role in the current management of CLL.5, 6 Moreover, PNA combinations with cyclophosphamide are more active compared with PNA monotherapy, as revealed in recent phase 3 prospective trials.7–10 However, numerous reports have indicated that patients with 17p13.1 deletions/TP53 abnormalities respond poorly to PNA, and most of those reports referred to FA monotherapy and FA combinations.7, 9–11 Those findings have translated into current opinion that patients with p53 dysfunction should be treated with novel p53-independent agents rather than PNAs.12

Little data are available on the clinical efficacy of 2-CdA or 2-CdA-based combinations in patients with 17p13.1/TP53 abnormalities; however, some differences in cytotoxicity mechanisms between 2-CdA and FA have been postulated.13 Unlike many other countries, in Poland, 2-CdA is more frequently used than FA in CLL, and the combination of 2-CdA with cyclophosphamide (the CC regimen) has become a widely used frontline treatment for younger patients.8 Taking this into consideration, we evaluated the outcome of first-line therapy with the CC regimen in patients with CLL who had the 17p13.1 deletion reported to Polish Adult Leukemia Group (PALG) registry.


Study Design

This study was a retrospective analysis that included all patients with CLL who were reported to the PALG registry between January 2004 and December 2007 and fulfilled 2 inclusion criteria: 1) they carried a 17p13.1 deletion, as determined by pretreatment FISH interphase cytogenetics; and 2) they were treated according to the CC protocol as upfront therapy. The diagnosis of CLL was based on the criteria established by the National Cancer Institute-Sponsored Working Group (NCI-WG).14 Pretreatment clinical staging was performed according to the Rai classification.15 Indications to start treatment for CLL were based on evidence of disease progression using previously reported criteria.8

Fluorescence In Situ Hybridization Analysis

FISH was performed on interphase nuclei of lymphocytes on blood smears before the start of the study treatment. Four commercial probes were used (Vysis, Bergish-Gladbach, Germany), including the microsatellite chromosome 12 probe D12Z3 and the unique sequence- or region-specific DNA probes p53 (17p13.1.1 locus), ATM (11q22.3 locus), and D13S319 (13q14.3 locus). Signals were counted in at least 200 interphase nuclei for each sample. To define the cutoff level for the deletions and trisomy 12, experiments were performed on peripheral blood smears from 10 healthy controls. A true deletion was considered to occur if the specimen under study exhibited greater than a mean ± standard deviation of 3 nuclei with only 1 signal (referring to deletions) or with 3 signals (referring to trisomy 12). On this basis, the cutoff level was set at 8.4% for 13q14 deletion, 8.8% for 11q22 deletion, 9.6% for 17p13.1 deletion, and 5% for trisomy 12.

Treatment Modality

The CC regimen consisted of 2-CdA 0.12 mg/kg over 30 minutes as an intravenous infusion and cyclophosphamide 250 mg/m2 intravenously, and both drugs were administered concurrently for 3 consecutive days. 2-CdA was available commercially from the Institute of Biotechnology and Antibiotics-Bioton (Warsaw, Poland). The CC cycles were repeated every 28 days up to maximum of 6 cycles. In patients who had severe, therapy-related infections or hematologic complications, the consecutive cycle was delayed until hematologic parameters improved or the patient recovered from infection. To prevent hyperuricemia, allopurinol was administered at dose of 300 mg daily. No routine prophylactic antibiotics, antiviral agents, or growth factors were administered. Patients who developed autoimmune hemolytic anemia (AIHA), immune thrombocytopenia (IT), or nonhematologic grade 3 or 4 toxicity during chemotherapy were excluded from further treatment with CC.

Response Criteria and Toxicity Monitoring

Treatment efficacy was assessed according to NCI-WG guidelines.14 A complete response (CR) required the absence of symptoms and organomegaly, a normal blood cell count (absolute lymphocyte count, <4 × 109/L; absolute neutrophil count, >1.5 × 109/L; hemoglobin concentration, >110 g/L; and platelet count, >100 × 109/L), bone marrow that contained <30% lymphocytes for at least 2 months, and no lymphoid infiltrate in bone marrow biopsy performed 2 months after clinical evidence of CR. Partial response (PR) criteria were a decrease ≥50% in the size of enlarged lymph nodes, spleen, and liver on physical examination and peripheral blood counts either identical to those for a CR or improved over pretreatment values by ≥50%. Patients with a nodular PR were analyzed as PRs. Hematologic toxicity was evaluated according to the criteria of the NCI-WG.14 Other side effects were assessed and monitored according to World Health Organization criteria. Infections were classified as treatment-related if they developed on treatment or within 4 months after the completion of chemotherapy.

Statistical Analysis

Progression-free survival (PFS) was defined as time from the start of the treatment to the time of disease progression, death, or last observation in remission. Overall survival (OS) was recorded as the time from treatment initiation to the time of either death from any cause or last contact. Probabilities of PFS and OS were estimated according to the Kaplan-Meier method and are given with 95% confidence intervals (95% CI).16 Statistical analyses were performed using the SPSS statistical software package for Windows (release 11.01; SPSS Inc., Chicago, Ill).


Patient Characteristics

In total, 20 patients with B-CLL who had 17p13.1 deletion and were treated upfront with CC were included in this study. Nine patients (45%) received therapy within an ongoing phase 3 PALG trial that compared the CC regimen to with FA plus cyclophosphamide (FC) in patients with previously untreated, progressive CLL (the PALG-CLL3 trial).17 The remaining 11 patients (55%) were treated outside clinical trials with an identical CC protocol. The analyzed group consisted of 13 men (65%) and 7 women (35%), and their median age at diagnosis was 59.4 years (range, 32.9-74.3 years). Patients' hematologic parameters at the start if therapy were as follows: median white cell blood count, 49.3 × 109/L (range, 15.7-358  × 109/L); median hemoglobin concentration, 14.1 g/dL (range, 10.4-15 g/dL); and median platelet count, 155 × 109/L (range, 12-264 × 109/L). On the basis of clinical and laboratory findings, 16 patients (80%) were classified with a low clinical stage (Rai 0-II), and the remaining 4 patients (20%) were classified with an advanced stage (Rai III or IV). The median disease duration from diagnosis to treatment initiation was 0.8 years (range, 0-1.7 years).

FISH analysis revealed 17p13.1 deletion as the sole aberration in malignant cells from 11 patients (55%). In blood samples from 9 patients (45%), additional aberrations were detected, including 13q14 deletion in 7 patients, 11q22 deletion in 1 patient, and trisomy 12 in 1 patient. Data on CD38 and ZAP-70 pretreatment expression levels were available in 3 patients, and IgVH mutational status was not evaluated in this patient group. The detailed baseline patient characteristics are shown in Table 1.

Table 1. Baseline Characteristics and Outcome of Treatment in Individual Patients
PatientSexAge, yWBC, ×109/LRai Stage% of CLL Cells With Del17p13.1Other FISH AberrationsNo. of CC CoursesResponse to CCResponse Duration, mo*Survival, mo
  • WBC, white blood cell count; CLL, chronic lymphocytic leukemia; Del, deletion; FISH, fluorescence in situ hybridization; CC, cladribine plus cyclophosphamide regimen; PR, partial response; CR, complete response; NR, nonresponse.

  • *

    Duration of response was measured from confirmation of response achievement to progression, death, or last contact.

7Man50111.0214Trisomy 126CR22≥28

Treatment Efficacy and Toxicity

The total number of administered CC cycles was 78 (median, 4 CC cycles per patient; range, 1-6 CC cycles per patient). Overall, 16 of 20 included patients responded to the CC regimen, yielding a significant overall response rate (ORR) of 80% (Table 2). A CR was confirmed in 10 patients (50%), and 6 patients (30%) achieved a PR. Responses to treatment in individual patients are listed in Table 1. The median PFS reached 23 months (95% CI, 5–41 months), and the median PFS was 0% at 3 years (Fig. 1A. The median OS was not reached during study follow-up at a median follow-up of 14 months. The predicted OS rate at 2 years was 52.5% (95% CI, 26%-79%) (Fig. 1B). Seven patients (35%) died during the study observation period.

Figure 1.

The probability of (Top) progression-free survival and (Bottom) overall survival in 20 patients who had chronic lymphocytic leukemia with 17p13.1 deletion and were treated according to the combined cladribine with cyclophosphamide protocol.

Table 2. Efficacy and Toxicity of First-Line Treatment With the Cladribine Plus Cyclophosphamide Regimen in 20 Patients With Chronic Lymphocytic Leukemia Who Had 17p13.1.1 Deletion Analyzed in the Current Study
VariableNo. of Patients (%)
  1. CC indicates cladribine plus cyclophosphamide regimen; WHO, World Health Organization.

Response to CC therapy, n=20 
 Complete response10 (50)
 Partial response6 (30)
 Nonresponse4 (20)
Toxicity of CC therapy 
 Neutropenia (WHO grade 3 and 4)3 (15)
 Thrombocytopenia (WHO grade2 (10)
 Anemia (WHO grade 3 and 4)2 (10)
 Infections (WHO grade 3 and 4)6 (30)

Treatment toxicity generally was acceptable and was similar to that reported previously in a larger group of patients that was treated according to the CC protocol.8, 17 No therapy-related deaths occurred. Of grade 3 and 4 toxicities, the most frequent were infections, which were diagnosed in 6 patients (30%) patients. Autoimmune complications were identified in 4 treated patients (20%) and included 2 episodes of AIHA and 2 episodes of IT. In 1 patient, Richter transformation was observed. The most common treatment side effects are listed in Table 2.


In this study, we observed that a relatively high proportion of patients with previously untreated CLL who had 17p13.1/TP53 deletion responded to the CC regimen. A response was observed in 80% of patients, and there was a significant CR rate of 50%. Our findings are of interest in the context of previous reports on the poor efficacy of PNAs and PNA combinations in p53-defective patients.7, 10, 11, 18, 19 In contrast to our results, in a United Kingdom CLL trial, no patients with TP53 deletion in >20% of CLL cells obtained a CR or a nodular PR with the FC regimen, and the predicted PFS in this group was 0% at 3 years.10 Similarly, a poor response to FA with cyclophosphamide and mitoxantrone was reported with no CRs in a Spanish single-arm study.20 Despite the relatively high ORR observed in our study, the remission durations were short, with a median PFS of 23 months and a median OS rate of 52.5% at 2 years (Fig. 1). This seems comparable to the response durations achieved with FC therapy. In the United States Intergroup trial E2997, the presence of 17p13.1 deletion was associated with a median PFS of 12 months in the FC arm.18 Furthermore, a German CLL trial comparing FC with FA revealed that, in patients who had the deletion, the median survival was only 15.9 months.19

It is noteworthy that a recent phase 3 trial produced longer responses with 2-CdA than with FA in patients with previously untreated CLL.21 In the last interim analysis of our ongoing PALG-CLL3 study, the global response rates were comparable in the CC and FC arms, but significantly more patients with 17p13.1 deletion responded to CC than to FC.22 However, it should be noted that the final results of this trial are not yet available, and the current numbers of patients with 17p13.1 deletion are relatively small. FA and 2-CdA are able to kill proliferating cells as well as quiescent cells, and they share similar complex and not fully understood mechanisms of cytotoxicity.23–25 The main mechanism is related to DNA damage leading to the induction of p53 and the intrinsic pathway of apoptosis activation.24 However, at least in resting cells, the cytotoxicity exerted by FA and 2-CdA also involves p53-independent pathways.25 In agreement with this finding, p53 abnormalities (including 17p13.1 deletion, TP53 mutations, and TP53+ promoter methylation) correlate with a poor response to FA but do not predict response in individual patients with CLL.26 More noteworthy are laboratory studies suggesting that 2-CdA and 2-chloro-2′-arafluoroadenine (clofarabine), but not FA, can induce cell death by direct mitochondrial injury, which may explain in part the potential differences in toxicity of 2-CdA and FA against p53-defective cells.13 Moreover, incomplete cross resistance between 2-CdA and FA in vitro and in vivo has been reported.27, 28

It is believed generally that p53-defective patients are unlikely to respond to conventional chemotherapy, including PNAs; thus, alternative non-p53-dependent agents are recommended.12 A humanized, anti-CD52 antibody, alemtuzumab, was able to induce a CR in some refractory patients with 17p13.1 deletion.29, 30 Other treatment options include high-dose corticosteroids, flavopiridol, and allogeneic stem cell transplantation with reduced-intensity conditioning regimens.31–34 Recently, Byrd and colleagues reported that combination of FA with an anti-CD20 antibody rituximab induced a PR in all 3 treated patients who had a 17p13.1 deletion, but the responses were of short duration.35 In our recent study, 34 of 46 patients (74%) who had heavily pretreated CLL responded to rituximab combined with 2-CdA (RC) or rituximab combined with CC and had a median PFS of 12 months, but FISH analysis was beyond the scope of that study.36 Whether such immunochemotherapy is more active against CLL with 17p13.1 deletion than classic PNA combinations needs to be verified in controlled randomized trials. Furthermore, the p53 dysfunction probably is not the only cause of drug resistance in CLL with 17p13.1 deletion, because it correlates with negative prognostic factors like as IgVH unmutated status, high ZAP-70 expression level, and chromosomal translocations.37, 38

In conclusion, this retrospective analysis demonstrated that the CC regimen induced a relatively high response rate in patients with previously untreated CLL patients who had 17p13.1/TP53 deletion, although the duration of the achieved responses and survival were not satisfactory. It is possible that a combination of the CC regimen with p53-independent agents may improve treatment results in this poor-risk patient population

Conflict of Interest Disclosures

Supported in part by the grants from the Ministry of Science, Warsaw Poland (2P05B01828) and the Medical University of Lodz (503-1093-1) and by the Foundation for the Development of Diagnostics and Therapy, Warsaw, Poland.