Purine analogues plus cyclophosphamide versus purine analogues alone for first‐line therapy of patients with chronic lymphocytic leukaemia

Abstract

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:

To assess and summarise the evidence for purine analogues plus cyclophosphamide compared with purine analogues alone for first‐line treatment of patients with CLL.

Background

Description of the condition

Definition and classification

Chronic lymphocytic leukaemia (CLL) is a lymphoproliferative disorder associated with a clonal expansion of morphologically mature but immunologically less mature lymphocytes. It manifests by progressive accumulation of these cells in the blood, bone marrow, and lymphatic tissues (Dighiero 2008). CLL usually presents with lymphocytosis, but lymphadenopathy, splenomegaly, anaemia and thrombocytopenia may occur during the course of the disease. Characteristic for the diagnosis of CLL is the presence of 5000 B lymphocytes/μl or more in the peripheral blood for the duration of at least 3 months (Hallek 2008). In addition, the World Health Organization (WHO) classification defined CLL as a mature B‐cell neoplasm, including small lymphocytic lymphoma (SLL). SLL is a different manifestation of the same neoplasm and is distinguishable from CLL by its leukaemic appearance (Campo 2011). We use the terms CLL and CLL/SLL interchangeably throughout this review.

Epidemiology

CLL accounts for approximately 25% of all leukaemias and is the most common lymphoid malignancy in Western countries (Chiorazzi 2005). The US incidence is 4.5 per 100,000 people per year (Howlader 2010). The incidence increases with age and the median age at diagnosis is approximately 70 years (Howlader 2010).

Staging and Prognosis

The disease is characterised by a highly variable clinical course and prognosis. Some patients may have no or minimal symptoms for many years with a normal life expectancy, without requiring treatment. Others are symptomatic at diagnosis or early thereafter. There are two established clinical staging systems: the Rai staging system (Rai 1975) and the Binet staging system (Binet 1981). The extent of the disease is reflected by enlargement of lymph nodes, liver, and spleen; the lymphocyte count in blood; and the degree of impairment of normal haematopoiesis. The two staging systems define three stages of disease, early (Rai 0; Binet A), intermediate (Rai I,II; Binet B), and advanced (Rai III/IV; Binet C), with substantial differences in clinical course and long‐term survival. These clinical staging systems are often of limited prognostic value at the time of diagnosis, when most patients are in the early stages of the disease (Hallek 2008; Robak 2009). Recently other prognostic factors have been identified which distinguish better between more and less active forms of the disease. In particular, patients with a 17p deletion have an aggressive form of the disease with a median survival time of less than one year (Dohner 2000).

Description of the intervention

Patients with CLL are treated when they have an intermediate or advanced stage of the disease with haematopoetic insufficiency or symptoms. Patients with asymptomatic early‐stage disease do not benefit from early treatment (CLL Trialists' Collaborative Group 1999; Dighiero 1998). Therefore the standard treatment of these patients is a watch and wait strategy.

First‐line standard treatment options for symptomatic patients include (Brugiatelli 2006; Eichhorst 2010; Hallek 2008; NCCN Guidelines 2011; Oscier 2004):

• monotherapy with: chlorambucil, bendamustine, or purine analogues (fludarabine, cladribine and pentostatine);

• polychemotherapies with: fludarabine with cyclophosphamide; cyclophosphamide, doxorubicin, vincristine, and prednisolone (CHOP) or cyclophosphamide, vincristine, and prednisolone (COP); and

• treatment with antibodies: such as alemtuzumab (anti‐CD52, Skoetz 2012); rituximab (anti‐CD20) or ofatumumab (anti‐CD20) which are most effective when they are given in addition to chemotherapeutics.

Steurer 2006 assessed the efficacy of single‐agent purine analogues compared to alkylating agents‐based treatment. The review showed statistically significantly higher response rates and longer progression‐free survival for patients with purine analogues, but no statistically significant improvement in overall survival.

Randomised controlled trials evaluated the efficacy of the combination of fludarabine with cyclophosphamide (FC) compared to fludarabine alone (F) (Eichhorst 2006; Flinn 2007). Within these trials patients receiving FC had a statistically significant benefit regarding the response rates (23% to 38% in the FC‐arm compared with 5% to 15% in the F‐arm) and the progression‐free survival (32 to 48 months compared with 19 to 20 months). The trials did not, however, show a statistically significant difference between both treatments with respect to overall survival (Eichhorst 2006; Flinn 2007). This observation (improved progression‐free survival without any benefit to overall survival for patients treated with purine analogues plus cyclophosphamide compared to purine analogues alone) was confirmed by a systematic review with IPD which included all randomised trials that began before 2004 (CLL Trialists’ Collaborative Group 2012).

Patients with CLL are at an increased risk of infection and infectious complications, including death. This may be related to the disease itself, the consequences of therapy, or both. Indeed, infections are more pronounced with more intensive treatments such as fludarabine, or the combination of fludarabine with cyclophosphamide (Hallek 2008).

How the intervention might work

Purine analogues are antimetabolites which mimic the structure of the metabolic purines. The most common three analogues used for the treatment of lymphoproliferative disorders are: Pentostatin (2´‐deoxycoformycin), cladribine (2‐chloro‐2´‐deoxyadenosine) and fludarabine (9‐B‐D‐arabinosyl‐2‐fluoroadanine) (Pettitt 2003). Several mechanisms were proposed to explain the antileukaemic activity of these substances. They induce inhibition of DNA synthesis and cell death through different mechanisms (Pettitt 2003), including the inhibition of DNA polymerase and ribonucleotide reductase (Genini 2000; Hartman 2004; Huang 2000) and the co‐operation with cytochrome c and apoptosis protein‐activated factor‐1 to initiate the intrinsic pathway of apoptosis (Ewald 2008; Genini 2000a; Leoni 1998).

Cyclophosphamide belongs to the group of alkylating agents. It is a prodrug that requires enzymatic and chemical activation. The resultant product (phosphoramide mustard) prevents cell division by cross‐linking DNA strands and decreasing DNA synthesis (Emadi 2009).

Purine analogues and alkylating agents have different mechanisms of action. Therefore, it is reasonable to combine these two substances in order to reach a synergistic effect. Additionally, an in vitro study showed that cyclophosphamide improves the cytotoxicity of fludarabine in B‐CLL cells due to an increased rate of fludarabine‐induced apoptosis of CD19(+) cells (Bellosillo 1999).

Treatment with purine analogues can induce a bone marrow suppression with a prolonged thrombocytopenia, neutropenia and anaemia. Other common side effects are infections (including opportunistic infections) due to a decrease in CD4+/CD8+ ratio (Robak 2005; Robak 2009). Cyclophosphamide toxicity depends on the dosage. Bone marrow suppression is the most common toxic effect, but nausea, vomiting, alopecia and gonadal failure are all common adverse effects (de Jonge 2005; Emadi 2009). Haemorrhagic cystitis has also been observed in patients treated with cyclophosphamide (Stillwell 1988). High doses are associated with cardiotoxicity (Gottdiener 1981; Murdych 2001).

Why it is important to do this review

The treatment of CLL is still a big challenge since it is the most common leukaemia in adults and it is currently incurable in most cases. As mentioned under Description of the intervention, purine analogues are an integral part of regimens for first‐line treatment of CLL.

Randomised controlled trials suggest an advantage of purine analogues plus cyclophosphamide compared with purine analogues alone, but none of them has demonstrated an improvement in overall survival (Eichhorst 2006; Flinn 2007). This Cochrane Review might provide a more definite answer with respect to overall survival.

Objectives

To assess and summarise the evidence for purine analogues plus cyclophosphamide compared with purine analogues alone for first‐line treatment of patients with CLL.

Methods

Criteria for considering studies for this review

Types of studies

We considered only randomised controlled trials as primary studies in this review (O'Connor 2011). We included both full text and abstract publications and excluded cross‐over studies and quasi‐randomised trials.

Types of participants

Male and female adults with previously untreated and histologically confirmed diagnosis of B‐CLL. If trials involve patients with different haematopoietic neoplasias, we used data from the B‐CLL subgroup. If subgroup data for CLL patients were not provided after contacting the study authors, we excluded the trial if less than 80% of patients have B‐CLL.

Types of interventions

We included trials assessing first‐line treatment only. This did not include maintenance therapy.

We included trials that compare following interventions:

• experimental intervention: Purine analogues in combination with cyclophosphamide; and

• comparator intervention: Purine analogues as a monotherapy (e.g. fludarabine, pentostatin, cladribine).

The purine analogues used must be equal in both arms within one study. Additional treatment such as supportive care or management of complications must also be equal in both arms. Antibody therapies (in both arms) were allowed.

Types of outcome measures

Primary outcomes

• Overall survival (OS), defined as the time interval from random treatment assignment/entry onto study to death from any cause or to last follow‐up

Secondary outcomes

• Complete response rate (CR)

• Tumour control outcomes such as time to progression (e.g. progression‐free survival (defined as time from randomisation to first evidence of progressive disease or death), or similar outcomes)

• Adverse effects (i.e. infections of WHO grade III or IV; serious adverse events; and all other adverse events of WHO grade III or IV)

• Treatment‐related mortality

• Health‐related quality of life was summarised, if available and measured with a reliable and valid questionnaire. In the case that different questionnaires were used, we reviewed the concept of measurement of these instruments to compare and, if possible, meta‐analysed their content

Search methods for identification of studies

Electronic searches

We adapted search strategies from those suggested in the Cochrane Handbook for Systematic Reviews of Interventions (Lefebvre 2011). We did not aply any language restriction to reduce the language bias.

We searched following databases:

• MEDLINE (1950 to present) (Appendix 1); and

• Cochrane Central Register of Controlled Trials (CENTRAL), The Cochrane Library, latest issue (Appendix 2).

Searching other resources

We searched following conference proceedings from 2000 to present, if they are not included in CENTRAL:

1. American Society of Hematology (ASH);

2. American Society of Clinical Oncology (ASCO);

3. European Hematology Association (EHA); and

4. European Society of Medical Oncology (ESMO).

Moreover we electronically searched the database of ongoing trials:

• Metaregister of controlled trials: http://www.controlled‐trials.com/mrct/.

In addition we looked for studies in the reference lists of relevant publications and we contacted pharmaceutical companies.

Data collection and analysis

Selection of studies

Initially two review authors (DVG, KB) independently screened all titles and abstracts of studies retrieved from the above sources. Clearly ineligible studies were rejected. We assessed the studies by using an eligibility form regarding study design and compliance with the following inclusion criteria.

1. Is the study described as randomised?

2. Were the patients diagnosed with B‐CLL?

3. Had the patients already received treatment? (if "yes", the study was excluded as we were interested in first‐line treatment only)

4. Were the patients in the intervention group treated with a combination of purine analogues and cyclophosphamide?

5. Were the patients in the control group treated only with purine analogues?

In case of doubt we included full text analysis and discussed eligibility with both review authors to finalise a decision (preferably including studies rather than losing relevant data). According to PRISMA we used a flow diagram to show numbers of identified records, excluded articles and included studies (Moher 2009).

Data extraction and management

Two review authors (DVG, KB) independently extracted data according to Chapter Seven of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011) by using a standardised data extraction form containing the following items:

• general information: author, title, source, publication date, country, language, duplicate publications;

• quality assessments: sequence generation, allocation concealment, blinding (participants, personnel, outcome assessors), incomplete outcome data, selective outcome reporting, other sources of bias;

• study characteristics: trial design, aims, setting and dates, source of participants, inclusion/exclusion criteria, comparability of groups, subgroup analysis, statistical methods, power calculations, treatment cross‐overs, compliance with assigned treatment, length of follow‐up, time point of randomisation;

• participant characteristics: age, gender, number of participants recruited / allocated / evaluated, participants lost to follow‐up, stage of the disease, date of diagnosis, co‐morbidities;

• interventions: dose and duration of the chemotherapy (schema), supportive treatment; and

• outcomes: overall survival (OS), complete response rate (CR), tumour control, adverse events (i.e. infections of WHO grade III or IV; serious adverse events; and all other adverse events of WHO grade III or IV), treatment‐related mortality, quality of life.

Assessment of risk of bias in included studies

To assess the methodological quality and the risk of bias we used a questionnaire according to the recommendations in Chapter Eight of the Cochrane Handbook for Systematic Reviews of Interventions for the following criteria (Higgins 2011a):

• sequence generation;

• allocation concealment;

• blinding (participants, personnel, outcome assessors);

• incomplete outcome data;

• selective outcome reporting; and

• other sources of bias.

The judgment of the review authors involved an answer for each criterion, based on a three‐point scale (low risk of bias, high risk of bias, or unclear) and a summary description.

Measures of treatment effect

For binary outcomes we calculated risk ratios with 95% confidence intervals for each trial. And for continuous outcomes we calculated standardised mean difference. For time‐to‐event outcomes we extracted the hazard ratio from published data according to Parmar 1998 and Tierney 2007.

Dealing with missing data

As suggested in Chapter 16 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011b) there are many potential sources of missing data which has to be taken into account: at study level; at outcome level; at summary data level; at individual level; at study‐level characteristics (e.g. for subgroups analysis). It is important to differentiate between "missing at random" and "not missing at random".

If data were assumed to be missing at random, we analysed only the available data (i.e. ignoring the missing data).

In the case data were assumed not to be missing at random, we imputed the missing data with replacement values, and treated these as if they were observed (e.g. last observation carried forward, imputing an assumed outcome such as assuming all were poor outcomes, imputing the mean, imputing based on predicted values from a regression analysis).

Assessment of heterogeneity

We assessed heterogeneity of treatment effects between trials by using a Chi² test with a significance level at P < 0.1. We used the I² statistic to quantify possible heterogeneity (30% < I² < 75%: moderate heterogeneity, 75% < I² : considerable heterogeneity) (Deeks 2011).

We used the test for interaction to test for differences between subgroup results.

Assessment of reporting biases

In meta‐analyses with at least 10 trials, we explored potential publication bias by generating a funnel plot and we statistically tested by means of a linear regression test. We considered P < 0.1 as significant for this test (Sterne 2011).

Data synthesis

We performed analyses according to the recommendations of Chapter Nine of the Cochrane Handbook for Systematic Reviews of Interventions (Deeks 2011).

We used aggregated data for analysis. For statistical analysis, we entered data into the Cochrane statistical package Review Manager (RevMan) 5. One review author entered data into the software and a second review author checked it for accuracy. We performed meta‐analyses using a fixed‐effect model (e.g. the generic inverse variance method for survival data outcomes and Mantel‐Haenszel method for dichotomous data outcomes). And we used the random‐effects model for the sensitivity analyses.

If appropriate, we calculated the number needed to treat to benefit and the number needed to treat to harm for our primary outcome OS.

We created a summary of findings table on absolute risks in each group with the help of GRADE. We summarised the evidence of OS, tumour control and adverse effects in this summary of findings table.

Subgroup analysis and investigation of heterogeneity

We assessed heterogeneity of treatment effects between trials by using a Chi² test with a significance level at P < 0.1. We used the I² statistic to quantify possible heterogeneity. We considered performing subgroup analyses on the following, if appropriate:

• different types of purine analogues;

• different stages of disease;

• antibody therapy (chemotherapy versus immunochemotherapy);

• age (younger 70 years of age versus older than 70 years of age); and

• prognostic factor (Del 17q versus no Del 17q).

We performed subgroup analyses for the following outcomes: overall survival, tumour control, infections, serious adverse events.

Sensitivity analysis

• Quality components, including full text publications versus abstracts, preliminary results versus mature results

• Random‐effects modelling

Appendices

Appendix 1. MEDLINE search strategy

1	exp Leukemia, Lymphocytic, Chronic, B‐Cell/
2	((leuk?em$ or leu?em$ or lymph$) adj (lymphocyt$ or lymphoblast$ or linfoid$ or b‐cell$)).tw,kf,ot.
3	(chronic$ or cronic$ or chroniq$ or well‐differential$).tw,kf,ot.
4	2 and 3
5	(lymphom$ and (small cell$ or small‐cell$)).tw,kf,ot.
6	(lymphom$ adj2 lymphocyt$).tw,kf,ot.
7	lymphoplasma?ytoid.tw,kf,ot.
8	cll.tw.
9	sll.tw.
10	or/5‐9
11	1 or 4 or 10
12	exp Antimetabolites/
13	(purin$ adj2 analog$).tw,kf,ot.
14	Pentostatin/
15	pentostatin$.tw,kf,ot.
16	lederl$.tw,kf,ot.
17	prasfarm$.tw,kf,ot.
18	supergen$.tw,kf,ot.
19	wyet$.tw,kf,ot.
20	nipet$.tw,kf,ot.
21	nipent$.tw,kf,ot.
22	deoxycoformycin$.tw,kf,nm,ot.
23	(ci‐825 or ci825).tw,kf,nm,ot.
24	(nsc‐218321 or nsc218321).tw,kf,nm,ot.
25	(pd‐81565 or pd81565).tw,kf,nm,ot.
26	(co‐vidarabin$ or covidarabin$).tw,kf,ot.
27	dcf$.tw,kf,ot.
28	or/12‐27
29	Cladribine/
30	cladribin$.tw,kf,ot.
31	litak$.tw,kf,ot.
32	movectro$.tw,kf,ot.
33	leustat$.tw,kf,ot.
34	chlorodeoxyadenosin$.tw,kf,nm,ot.
35	deoxyadenosin$.tw,kf,nm,ot.
36	chloroadenosin$.tw,kf,nm,ot.
37	(2‐cda$ or 2cda$).tw,kf,nm,ot.
38	(rwj‐26251$ or rwj26251$).tw,kf,nm,ot.
39	or/29‐38
40	Fludarabin$.tw,kf,ot.
41	fludara$.tw,kf,ot.
42	fluoro‐ara$.tw,kf,nm,ot.
43	amp$.tw,kf,nm,ot.
44	famp$.tw,kf,nm,ot.
45	or/40‐44
46	28 or 39 or 45
47	11 and 46
48	randomized controlled trial.pt.
49	controlled clinical trial.pt.
50	randomized.ab.
51	placebo.ab.
52	drug therapy.fs.
53	randomly.ab.
54	trial.ab.
55	groups.ab.
56	or/48‐55
57	humans.sh.
58	56 and 57
59	47 and 58

Appendix 2. CENTRAL search strategy

#1	MeSH descriptor Leukemia, B‐Cell explode all trees
#2	MeSH descriptor Leukemia, Lymphocytic, Chronic, B‐Cell explode all trees
#3	(leu*em* NEAR/ lymphocyt*) or (leu*em* NEAR/ lymphoblast*) or (leu*em* NEAR/ linfoid*) or (leu*em* NEAR/ b‐cell*)
#4	(leu*em* NEAR/ lymphocyt*) or (leu*em* NEAR/ lymphoblast*) or (leu*em* NEAR/ linfoid*) or (leu*em* NEAR/ b‐cell*)
#5	(lymph* NEAR/ lymphocyt*) or (lymph* NEAR/ lymphoblast*) or (lymph* NEAR/ linfoid*) or (lymph* NEAR/ b‐cell*)
#6	(chronic*) or (cronic*) or (chroniq*) or (well‐differential*)
#7	(#6 AND ( #3 OR #4 OR #5 ))
#8	(lymphom*) and (small cell* or small‐cell*)
#9	(lymphom* NEAR/2 lymphocyt*)
#10	(lymphoplasma*ytoid*)
#11	(cll or sll)
#12	(#1 OR #2 OR #7 OR #8 OR #9 OR #10 OR #11)
#13	MeSH descriptor Antimetabolites explode all trees
#14	purin* near/2 analog*
#15	MeSH descriptor Pentostatin explode all trees
#16	pentostatin*
#17	lederl*
#18	prasfarm*
#19	supergen*
#20	wyet*
#21	nipet*
#22	nipent*
#23	deoxycoformycin*
#24	(ci‐825 or ci825)
#25	(nsc‐218321 or nsc218321)
#26	(pd‐81565 or pd81565)
#27	(co‐vidarabin* or covidarabin*)
#28	dcf*
#29	(#14 OR #15 OR #16 OR #17 OR #18 OR #19 OR #20 OR #21 OR #22 OR #23 OR #24 OR #25 OR #26 OR #27 OR #28)
#30	MeSH descriptor Cladribine explode all trees
#31	cladribin*
#32	litak*
#33	movectro*
#34	leustat*
#35	chlorodeoxyadenosin*
#36	deoxyadenosin*
#37	chloroadenosin*
#38	(2‐cda* or 2cda*)
#39	(rwj‐26251* or rwj26251*)
#40	(#30 OR #31 OR #32 OR #33 OR #34 OR #35 OR #36 OR #37 OR #38 OR #39)
#41	Fludarabin*
#42	fludara*
#43	fluoro‐ara*.
#44	amp*
#45	amp*
#46	(#41 OR #42 OR #43 OR #44 OR #45)
#47	(#29 OR #40 OR #46)
#48	(#12 AND #47)
#49	"accession number" near pubmed
#50	(#48 AND NOT #49)

 

What's new

Date	Event	Description
28 December 2016	Amended	withdrawn

Contributions of authors

Dagmar Villarroel Gonzalez: developed and wrote the first and final draft of the protocol

Ina Monsef: Trials Search Co‐ordinator

Thomas Elter: provided clinical expertise, proof read and commented on the first and final draft

Andreas Engert: provided clinical expertise, proof read and commented on the first and final draft

Nicole Skoetz: provided methodological expertise, proof read and commented on the first and final draft

Sources of support

Internal sources

• Cochrane Haematological Malignancies Group, Department I of Internal Medicine, University Hospital of Cologne, Germany.

External sources

• No sources of support supplied

Declarations of interest

Dagmar Villarroel Gonzalez: none known

Thomas Elter: "As a member of the German CLL Study Group, I received honoraria and travel/accommodation/meeting expenses for presenting CLL‐related data."

Ina Monsef: none known

Andreas Engert: none known

Nicole Skoetz: none known

Notes

Authors made no progress within the last 12 months.

Withdrawn from publication for reasons stated in the review