Rituximab, ofatumumab and other monoclonal anti-CD20 antibodies for chronic lymphocytic leukaemia

BACKGROUND

Chronic lymphocytic leukaemia (CLL) accounts for 25% of all leukaemias and is the most common lymphoid malignancy in western countries. Standard treatments include mono- or polychemotherapies, usually combined with monoclonal antibodies such as rituximab or alemtuzumab. However, the impact of these agents remains unclear, as there are hints for increased risk of severe infections.

OBJECTIVES

The objectives of this review are to provide an evidence-based answer regarding the clinical benefits and harms of monoclonal anti-CD20 antibodies (such as rituximab, ofatumumab, GA101) compared to no further therapy or to other anti-leukaemic therapies in patients with CLL, irrespective of disease status.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 12, 2011), MEDLINE (from January 1990 to 4 January 2012), and EMBASE (from 1990 to 20 March 2009) as well as conference proceedings (American Society of Hematology, American Society of Clinical Oncology, European Hematology Association and European Society of Medical Oncology) for randomised controlled trials (RCTs).

SELECTION CRITERIA

We included RCTs examining monoclonal anti-CD20 antibodies compared to no further therapy or to anti-leukaemic therapy such as chemotherapy or monoclonal antibodies in patients with newly diagnosed or relapsed CLL.

DATA COLLECTION AND ANALYSIS

We used hazard ratios (HR) as effect measures for overall survival (OS), progression-free survival (PFS) and time to next treatment, and risk ratios (RR) for response rates, treatment-related mortality (TRM) and adverse events (AEs). Two review authors independently extracted data and assessed quality of trials.

MAIN RESULTS

We screened a total of 1150 records. Seven RCTs involving 1763 patients were identified, but only five could be included in the two separate meta-analyses we performed. We judged the overall the quality of these trials as moderate to high. All trials were randomised and open-label studies. However, two trials were published as abstracts only, therefore we were unable to assess the potential risk of bias for these trials in detail.Three RCTs (N = 1421) assessed the efficacy of monoclonal anti-CD20 antibodies (i.e. rituximab) plus chemotherapy compared to chemotherapy alone. The meta-analyses showed a statistically significant OS (HR 0.78, 95% confidence interval (CI) 0.62 to 0.98, P = 0.03, the number needed to treat for an additional beneficial effect (NNTB) was 12) and PFS (HR 0.64, 95% CI 0.55 to 0.74, P < 0.00001) advantage for patients receiving rituximab. In the rituximab-arm occurred more AEs, World Health Organization (WHO) grade 3 or 4 (3 trials, N = 1398, RR 1.15, 95% CI 1.08 to 1.23, P < 0.0001; the number needed to harm for an additional harmful outcome (NNTH) was 9), but that did not lead to a statistically significant difference regarding TRM (3 trials, N = 1415, RR 1.19, 95% CI 0.70 to 2.01, P = 0.52).Two trials (N = 177) evaluated rituximab versus alemtuzumab. Neither study reported OS or PFS. There was no statistically significant difference between arms regarding complete response rate (CRR) (RR 1.21, 95% CI 0.94 to 1.58, P = 0.14) or TRM (RR 0.31, 95% CI 0.06 to 1.51, P = 0.15). However, the CLL2007FMP trial was stopped early owing to an increase in mortality in the alemtuzumab arm. More serious AEs occurred in this arm (43% with alemtuzumab versus 22% with rituximab; P = 0.006).Two trials assessed different dosages or time schedules of monoclonal anti-CD20 antibodies. One trial (N = 104) evaluated two different rituximab schedules (concurrent arm: fludarabine plus rituximab (Flu-R) plus rituximab consolidation versus sequential arm: fludarabine alone plus rituximab consolidation). The comparison of the concurrent versus sequential regimen of rituximab showed a statistically significant difference of the CRR with 33% in the concurrent-arm and 15% in the sequential-arm (P = 0.04), that did not lead to statistically significant differences regarding OS (HR 1.14, 95% CI 0.20 to 6.65, P = 0.30) or PFS (HR 0.96, 95% CI 0.43 to 2.15, P = 0.11). Furthermore results showed no differences in occurring AEs, except for neutropenia, which was more often observed in patients of the concurrent arm. The other trial (N = 61) investigated two different dosages (500 mg and 1000 mg) of ofatumumab in addition to FluC. The arm investigating ofatumumab did not assess OS and a median PFS had not been reached owing to the short median follow-up of eight months. It showed no statistically significant differences between arms regarding CRR (32% in the FCO500 arm versus 50% in the FCO1000 arm; P = 0.10) or AEs (anaemia, neutropenia, thrombocytopenia).

AUTHORS' CONCLUSIONS

This meta-analysis showed that patients receiving chemotherapy plus rituximab benefit in terms of OS as well as PFS compared to those with chemotherapy alone. Therefore, it supports the recommendation of rituximab in combination with FluC as an option for the first-line treatment as well as for the people with relapsed or refractory CLL. The available evidence regarding the other assessed comparisons was not sufficient to deduct final conclusions.

Alemtuzumab for patients with chronic lymphocytic leukaemia

BACKGROUND

Chronic lymphocytic leukaemia (CLL) accounts for 25% of all leukaemias and is the most common lymphoid malignancy in Western countries. Standard treatment  includes mono- or poly-chemotherapies. Nowadays, monoclonal antibodies are added, especially alemtuzumab and rituximab. However, the impact of these agents remains unclear, as there are hints of an increased risk of severe infections.

OBJECTIVES

To assess alemtuzumab compared with no further therapy, or with other anti-leukaemic therapy in patients with CLL.

SEARCH METHODS

We searched CENTRAL and MEDLINE (from January 1985 to November 2011), and EMBASE (from 1990 to 2009) as well as conference proceedings for randomised controlled trials (RCTs). Two review authors (KB, NS) independently screened search results.

SELECTION CRITERIA

We included RCTs comparing alemtuzumab with no further therapy or comparing alemtuzumab with anti-leukaemic therapy such as chemotherapy or monoclonal antibodies in patients with histologically-confirmed B-cell CLL. Both pretreated and chemotherapy-naive patients were included.

DATA COLLECTION AND ANALYSIS

We used hazard ratios (HR) as an effect measure for overall survival (OS) and progression-free survival (PFS) and risk ratios (RRs) for response rates, treatment-related mortality (TRM) and adverse events. Two review authors independently extracted data and assessed the quality of trials.

MAIN RESULTS

Our search strategies led to 1542 potentially relevant references. Of these, we included five RCTs involving 845 patients. Overall, we judged the quality of the five trials as moderate. All trials were reported as randomised and open-label studies. However, two trials were published as abstracts only, therefore, we were unable to assess the potential risk of bias for these trials in detail. Because of the small number of studies in each analysis (two), the quantification of heterogeneity was not reliable.Two trials (N = 356) assessed the efficacy of alemtuzumab compared with no further therapy. One trial (N = 335), reported a statistically significant OS advantage for all patients receiving alemtuzumab (HR 0.65 (95% confidence interval (CI) 0.45 to 0.94; P = 0.021). However, no improvement was seen for the subgroup of patients in Rai stage I or II (HR 1.07; 95% CI 0.62 to 1.84; P = 0.82). In both trials, the complete response rate (CRR) (RR 2.61; 95% CI 1.26 to 5.42; P = 0.01) and PFS (HR 0.58; 95% CI 0.44 to 0.76; P < 0.0001) were statistically significantly increased under therapy with alemtuzumab. The potential heterogeneity seen in the forest plot could be due to the different study designs: One trial evaluated alemtuzumab additional to fludarabine as relapse therapy; the other trial examined alemtuzumab compared with no further therapy for consolidation after first remission.There was no statistically significant difference for TRM between both arms (RR 0.57; 95% CI 0.17 to 1.90; P = 0.36). A statistically significant higher rate of CMV reactivation (RR 10.52; 95% CI 1.42 to 77.68; P = 0.02) and infections (RR 1.32; 95% CI 1.01 to 1.74; P = 0.04) occurred in patients receiving alemtuzumab. Seven severe infections (64%) in the alemtuzumab arm in the GCLLSG CLL4B study led to premature closure.Two trials (N = 177), evaluated alemtuzumab versus rituximab. Neither study reported OS or PFS. We could not detect a statistically significant difference for CRR (RR 0.85; 95% CI 0.67 to 1.08; P = 0.18) or TRM (RR 3.20; 95% CI 0.66 to 15.50; P = 0.15) between both arms. However, the CLL2007FMP trial was stopped early due to an increase in mortality in the alemtuzumab arm. More serious adverse events occurred in this arm (43% versus 22% (rituximab), P = 0.006).One trial (N = 297), assessed the efficacy of alemtuzumab compared with chemotherapy (chlorambucil). For this trial, no HR is reported for OS. Median survival has not yet been reached, 84% of patients were alive in each arm at the data cut-off or at the last follow-up date (24.6 months). The TRM between arms shows no statistical significant difference (0.6% versus 2.0%; P = 0.34). Alemtuzumab statistically significantly improves PFS (HR 0.58; 95% CI 0.43 to 0.77; P = 0.0001), time to next treatment (23.3 compared with 14.7 months; P = 0.0001), ORR (83.2% versus 55.4%; P < 0.0001), CRR (24.2% versus 2.0%; P < 0.0001), and minimal residual disease rate (7.4% versus 0%; P = 0.0008) compared with chlorambucil. Statistically, significantly more asymptomatic (51.7% versus 7.4%) and symptomatic cytomegalovirus (CMV) infections (15.4% versus 0%) occurred in the patients treated with alemtuzumab.

AUTHORS' CONCLUSIONS

In summary, the currently available evidence suggests an OS, CRR and PFS benefit for alemtuzumab compared with no further therapy, but an increased risk for infections in general, CMV infections and CMV reactivations. The role of alemtuzumab versus rituximab still remains unclear, further trials with longer follow-up and overall survival as primary endpoint are needed to evaluate the effects of both agents compared with each other. Alemtuzumab compared with chlorambucil seems to be favourable in terms of PFS, but a longer follow-up period and trials with overall survival as primary endpoint are needed to determine whether this effect will translate into a survival advantage.