Although the introduction of purine analogues, such as fludarabine, has made it possible to treat especially younger patients with chronic lymphocytic leukaemia (CLL) more effectively compared with alkylating agents, relapses inevitably occur in most cases. The majority of previously untreated patients achieving complete remission after fludarabine-based chemotherapy will relapse after a median period of 20–48 months (Rai et al, 2000; Leporrier et al, 2001; Eichhorst et al, 2006; Catovsky et al, 2007). This is mainly because of the proliferation of residual malignant cells escaping control by induction chemotherapy. Therefore, the detection and eradication of minimal residual disease (MRD) is critical for the prevention of relapse and the achievement of a long-term remission. Alemtuzumab, a humanized monoclonal antibody targeting the CD52 antigen that is approved for use in CLL, has been shown to improve the quality of responses when used as consolidation therapy in patients responding to first-line treatment (O’Brien et al, 2003; Wendtner et al, 2004; Montillo et al, 2006). However, recent reports about increased toxicity after alemtuzumab consolidation have stressed the necessity of further trials evaluating adequate consolidation regimens based on alemtuzumab (Lin et al, 2007; Hainsworth et al, 2008). Here we report long-term survival data based on a randomized phase III trial that investigates the role of alemtuzumab consolidation therapy in patients in first remission after fludarabine-based first-line chemotherapy.
Alemtuzumab has shown considerable activity in untreated and relapsed chronic lymphocytic leukaemia. We report our long-term experience in 21 patients within a randomized phase III trial investigating the role of alemtuzumab for consolidation therapy after first-line fludarabine ± cyclophosphamide, which was stopped prematurely due to severe infections. However, after a median follow-up of 48 months, progression-free survival was significantly prolonged for patients receiving alemtuzumab consolidation compared to those with no further treatment (P = 0·004). Minimal residual disease (MRD) levels were persistently reduced after consolidation. Therefore, despite toxicity, MRD reduction by alemtuzumab consolidation translates into a significantly improved long-term clinical outcome.
Study design and treatment
Patients (18–65 years) with CLL in complete or partial remission according to the National Cancer Institute working group criteria (Cheson et al, 1996) after fludarabine (F) or fludarabine/cyclophosphamide (FC) first-line treatment were eligible to enter this open-label, randomized phase III trial (CLL4B) conducted by the German CLL Study Group (GCLLSG), as previously reported (Wendtner et al, 2004). Briefly, patients were randomized for treatment with alemtuzumab (30 mg t.i.w. for a maximum of 12 weeks) or observation. Alemtuzumab had to be started between 30 and 90 d after the last dose of F or FC. Anti-infective prophylaxis including cotrimoxazole (960 mg p.o., b.i.d., t.i.w.) and famciclovir (250 mg p.o., b.i.d) was given during and up to a minimum of 2 months following the discontinuation of alemtuzumab therapy. The primary end-point of the trial was progression-free survival (PFS), defined as the time between start of F or FC until disease progression. The trial was carried out according to the Helsinki Declaration of 1975, as revised in 2000. Approval was obtained from the local ethics committee and the institutional review board of the Ludwig-Maximilians-University, Munich. All patients gave written informed consent prior to enrolment.
Staging, follow-up and detection of minimal residual disease
Staging and follow-up assessments including physical examination, ultrasound and/or computed tomography scans were performed every 3 months while bone marrow examination was only recommended for patients with clinical complete response (CR). Peripheral blood was collected for MRD analysis by real-time quantitative polymerase chain reaction (RQ-PCR) and was scheduled for months 3, 6, 12, 18 and 24 after randomization. RQ-PCR was performed using an upstream allele-specific primer (ASO-primer) matching the clonotypic CDR3 region and a consensus downstream JH primer and TaqMan-probe combination (Bruggemann et al, 2000). Standard curves were generated by diluting DNA from samples taken at the time of primary diagnosis into polyclonal genomic DNA. Clonotypic CD3 copy numbers were normalized by the copy number of the albumin gene quantified by an albumin-specific TaqMan assay (Ritgen et al, 2004). The sensitivity for each individual patient was between 1 × 10−4 and 1 × 10−5.
Time to event was estimated with the Kaplan–Meier method, differences tested with the log-rank test. Based on a sample size of 45 patients for each arm, the log-rank test was selected with a power of 80% to detect a 20% difference of PFS at 24 months between the two trial arms, based on 47 months overall length of the trial. Fisher’s exact test was used to compare qualitative parameters between subgroups of patients. A statistical significance was accepted for P < 0·05.
Results and discussion
The trial was stopped prematurely because of severe infections [seven Common Toxicity Criteria (CTC) grade III infections, which included four cytomegalovirus reactivations and one CTC IV infection because of a pulmonary aspergillosis] in 7/11 patients treated with alemtuzumab (Wendtner et al, 2004). These infections were successfully treated and not associated with the cumulative dose of alemtuzumab. With the exception of an oropharyngeal papillomatosis seen in one patient 11 months after discontinuation of alemtuzumab, no late complications of consolidation therapy have been documented. Of 21 evaluable responding patients after first-line F or FC, 11 patients [one CR, one nodular partial response (nPR), nine partial response (PR)] had been randomized to alemtuzumab consolidation treatment. After a median follow-up of 48 months, calculated from time of randomization within this trial, the median PFS was significantly improved for patients who had received alemtuzumab consolidation compared to those who had received no further treatment (not reached versus 20·6 months, P = 0·004). The 3-year PFS at month 36 after randomization was 81·8% for patients in the alemtuzumab arm versus 30·0% in the observation arm. Median PFS from the beginning of induction therapy with F or FC (median follow-up 54·8 months) was also significantly prolonged in favour of patients consolidated with alemtuzumab (not reached versus 27·7 months, P = 0·01). Accordingly, the 3-year PFS at month 36 after start of induction treatment was 90·9% for patients after alemtuzumab versus 40·0% after observation. To date, three of 11 patients have presented with disease progression after alemtuzumab consolidation compared with 8/10 progressing patients in the observation arm (Table SI). Differences in PFS between both arms were not associated with disease stage before first line treatment, type of first line chemotherapy (F vs. FC), response status before initiation of consolidation therapy (CR vs. nPR vs. PR), IGHV mutational status or cytogenetic aberrations (P > 0·10). With the exception of two patients who died because of progressive disease (one patient in each arm) all patients were alive at last follow-up (Fig 1, Table SI).
Consolidation therapy with alemtuzumab induced pronounced reductions in MRD levels along with clinical remissions in CLL patients. All patients who received alemtuzumab and for whom MRD data were available, became MRD-negative during treatment and showed a MRD decrement in peripheral blood from a median level of 2·2 × 10−3 after first-line treatment to a median level of 5 × 10−5 (Fig 2). One patient (patient 3; Fig 2) with an 11q- deletion and unmutated IGHV status showed a rapid increase of MRD after completion of alemtuzumab consolidation, whereas the majority showed stable or only moderate increase of MRD during follow-up of about 18 months. Two patients (patients 2 and 5; Fig 2) exhibited long lasting MRD negativity during the maximum observation period of 15 and 30 months respectively. Thus, quality of MRD reduction achieved with alemtuzumab consolidation was similar to that observed after autologous stem cell transplantation as recently described (Ritgen et al, 2004).
This trial was stopped prematurely because of the occurrence of severe acute infections in seven patients. The high incidence of infections may have been due, in part, to the short time interval between initiation of alemtuzumab and the last dose of fludarabine (median 67 d), which may not have been sufficient to allow recovery from myelosuppression. However, the addition of alemtuzumab as a consolidation regimen following remission induction by fludarabine or fludarabine plus cyclophosphamide was judged to have been highly effective and led to sustained MRD reduction, which translated into significantly improved clinical outcome. The extended duration of remission and the encouraging molecular responses noted in this trial has prompted the GCLLSG to initiate a new phase I/II alemtuzumab dose-finding study in CLL patients after induction of clinical remission by fludarabine-based therapy. Data from other clinical trials have also demonstrated an improvement in the number and quality of clinical responses with alemtuzumab consolidation therapy after fludarabine-based chemotherapy of CLL (O’Brien et al, 2003; Montillo et al, 2006). In a phase II trial conducted by the M.D. Anderson Cancer Center, alemtuzumab improved the overall response rate in 46% of patients and molecular remission was achieved in 38% of patients (O’Brien et al, 2003). Another trial has shown that first-line fludarabine therapy followed by alemtuzumab consolidation is feasible for subsequent peripheral blood stem cell collection and autologous transplantation. Following alemtuzumab consolidation, the CR rate increased from 35% to almost 80% while 56% of assessable patients achieved MRD negativity (Montillo et al, 2006). Although based on a low sample size, our randomized phase III trial demonstrated for the first time that an improved clinical and molecular response rate after alemtuzumab consolidation also translates into a survival advantage for these patients.
In summary, alemtuzumab consolidation provides a significant improvement in the quality of clinical responses by eradicating MRD and achieving at least temporarily molecular remissions. Although alemtuzumab consolidation seems to have the potential to increase PFS, it is not yet a standard of care in CLL. This approach has been associated with a risk of infectious events, especially when it was administered within a short-time interval following induction therapy and possibly, when alemtuzumab was used after induction chemoimmunotherapy including rituximab (Lin et al, 2007; Hainsworth et al, 2008). Ongoing and future trials will need to solve open issues regarding optimal timing, schedule and dosage of alemtuzumab consolidation therapy.
This study was supported in part by research funding from BayerSchering AG, Berlin, and MedacSchering Onkologie, Munich, Germany to MH and CMW.
C.D.S., B.F.E. and W.A. were responsible for patient accrual, monitored the trial and analysed the data. R.B. was responsible for data collection and conducted the statistical analyses of the trial. M.R. and M.K. were responsible for the MRD analyses within this trial. M.H. designed and supervised the trial. C.M.W. analysed the data, supervised the trial and wrote the manuscript together with C.D.S.