Acute Myeloid Leukaemia

Long-term outcome after allogeneic hematopoietic stem cell transplantation for advanced stage acute myeloblastic leukemia: a retrospective study of 379 patients reported to the Société Française de Greffe de Moelle (SFGM)

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Abstract

To assess the place of allogeneic hematopoietic stem cell transplantation (HSCT) in the advanced stage of acute myeloid leukemia (AML), we retrospectively analyzed 379 consecutive patients who underwent allogeneic HSCT for advanced AML. The median follow-up of the entire cohort was 7.5 years. Sixty-nine patients (18%) were transplanted with primary resistant disease. Three hundred and ten (82%) were relapsed patients, 94 (30%) of whom were in untreated relapse, 67 (22%) in refractory relapse and 149 (48%) in 2nd or 3rd complete remission at time of transplantation. The 5-year probabilities of overall survival (OS), disease-free survival (DFS), and transplant-related mortality (TRM) were 22 ± 4% 20 ± 4%, 45 ± 6%, respectively. In multivariate analysis, we demonstrated the favorable impact on OS, DFS and TRM of two factors over which we have no control (age <15 years, complete remission achievement) and three factors over which we have some control (female donor, acute and chronic graft-versus-host disease). The results of this study suggest that the graft-versus-leukemia effect is important in advanced AML and that new HSCT modalities are needed for some patients with this indication. Bone Marrow Transplantation (2000) 26, 1157–1163.

Main

The outcome of treatment in younger patients with de novo acute myeloid leukemia (AML) has improved substantially over the past decade. Complete remission (CR) rates range from 60% to 80% with long-term survival in about 50% of cases. Advances can be attributed to several factors related to supportive care, which has allowed the safer use of more intensive chemotherapy schedules.12 Myeloablative therapy followed by allogeneic hematopoietic stem cell transplantation (HSCT) has also proven to be a very effective therapy.34 Despite these results, patients with AML can still fail to achieve CR or can relapse after first-line therapy within 2 years of CR achievement. These patients have a very poor prognosis and it is generally accepted that few cases can be cured at this stage using chemotherapy alone.5 Indeed, even though the best strategy regarding postremission therapy in first CR is still subject to controversy,6 allogeneic bone marrow transplantation has shown a potential for cure at time of relapse.78 Although allogeneic HSCT has frequently been indicated in recurrent or refractory AML, very few large series allowing prognostic factor analysis have been reported. In this retrospective study, we analyzed the impact of pre- and post-transplantation factors on the outcome of allogeneic transplants in 379 consecutive patients with advanced stage AML whose cases were reported to the Société Française de Greffe de Möelle (SFGM) registry from 1980 to 1993.

Patients and methods

Patients and disease characteristics

Between 1980 and 1993, 379 patients (212 males and 167 females) with advanced AML underwent allogeneic HSCT (Table 1). Sixty-nine patients presented with primary resistant disease (Pr) and 310 were in relapse after having achieved complete remission (CR) by chemotherapy alone. Among these 310 patients, 277 were in first relapse, 31 were in second relapse, and two were in third relapse. The pretransplantation stage of these 310 relapsed AML patients was as follows: untreated relapse (UR) in 94 cases, refractory relapse (RR) in 67 cases, and 2nd or 3rd CR in 149 cases. The median follow-up of the entire cohort was 7.5 years (range 2–15 years). Fifty-six patients received transplants between 1980 and 1984, 178 patients between 1985 and 1989 and 145 patients between 1990 and 1993. The median age was 28 years (range 2 months to 58 years). Three hundred and thirty-two patients were morphologically classified according to the FAB classification.9 There were 63 M1, 103 M2, 31 M3, 57 M4, 62 M5 and 16 M6. All data were prospectively reported to SFGM registry from 33 centers and were completed by additional data obtained from questionnaires sent to each center.

Table 1  Patient characteristics and transplantation procedures

Transplant procedures

Three hundred and fifty patients received transplants from related donors: 313 from HLA-identical sibling donors, five from twins, one from a phenotypically identical donor and 31 from HLA mismatched related donors (Table 1). Twenty-nine patients received transplants from unrelated donors: 28 from HLA A, B and DRB1 identical donors and one from a one-antigen mismatched donor. Two hundred and ninety-nine patients (79%) received a conditioning regimen based on total body irradiation (TBI). TBI was fractionated in 134 patients. Eighty patients (21%) received an intensive chemotherapy-based conditioning regimen. Two hundred and eighty-six patients (75%) received a standard conditioning regimen of cyclophosphamide associated with either busulfan or TBI, while 93 patients (25%) received an intensified preparatory regimen. Graft-versus-host disease (GVHD) prophylaxis was administered in 363 patients (96%): 32 patients (9%) received cyclosporine alone, 56 patients (15%) received methotrexate alone, and 236 patients (65%) were treated with a combination of cyclosporine and methotrexate. Thirty-nine (11%) patients received a T cell-depleted graft.

Statistical analysis

The primary endpoints of this study were overall survival (OS), disease-free survival (DFS) and transplant-related mortality (TRM). Survival duration was measured from the time of transplantation to the time of death or last follow-up. We calculated DFS in patients who achieved a CR from the time of CR to the time of relapse, death from any cause, or last follow-up. TRM was defined as mortality exclusively related to the transplant. Patients surviving more than 21 days after transplantation with evidence of engraftment were considered at risk for acute GVHD. We diagnosed chronic GVHD as occurring in patients surviving more than 90 days after transplantation. Relapse was defined as a hematological or clinical recurrence at any site. We used the Kaplan–Meier product-limit estimate method to calculate OS, DFS and TRM probabilities.10 Survival curves were compared using the log-rank test.11 Parameters were analyzed for potential prognostic significance for CR achievement, TRM, DFS and OS. We analyzed separately three sets of factors: (1) factors over which we have absolutely no control (age, FAB classification, AML stage, duration of CR); (2) factors over which we have some control (donor sex, HLA compatibility, acute GVHD, and chronic GVHD); and (3) factors over which we have total control (T depletion and conditioning regimen).

In the analysis, qualitative variables were treated as dichotomous with cut-off points at the approximate median value, or were compared using a t-test. Prognostic factors for CR were studied using stepwise multiple logistic regression and prognostic factors for TRM, DFS, and OS were studied using the stepwise Cox proportional hazard model.12 All variables that were statistically predictive for survival rates and their interactions were proposed for entry in the stepwise multivariate model for prediction of the same endpoint. We tested how well the models fit using the likelihood ratio statistics. All calculations were performed using BMDP PC-90 statistical program (BMDP Statistical Software, Los Angeles, CA, USA).

Results

Post-transplant response

One hundred and forty-nine patients underwent allogeneic HSCT after achieving a second or a third CR with chemotherapy. Allogeneic HSCT was also performed in 69 patients with primary resistant AML, and in 94 and 67 patients respectively with untreated or refractory relapse.

Transplantation allowed CR achievement in 53/69 patients (77%) with primary resistant (Pr) disease, 50/67 patients (75%) with RR, and in 75/94 patients (80%) with UR.

Post-transplant outcome

At a median follow-up date 7.5 years after transplant (range 2–15 years), 77 patients were still alive. The 5-year probabilities of OS, DFS, and TRM were 22 ± 4%, 20 ± 4%, 45 ± 6%, respectively. The 5-year probability of survival for patients who had received an allotransplant in CR (35 ± 8%) was significantly better (P = 0.0001) than for patients transplanted in Pr disease (13 ± 8%) or for patients undergoing transplantation in UR or RR (14 ± 6% and 11 ± 6% respectively) (Figure 1). The DFS was better when allogeneic HSCT (5-year probability 32 ± 6%) was performed in CR than when HSCT was performed in Pr, UR, or RR (9 ± 6%, 13 ± 6%, 11 ± 6%) (P = 0.001). We observed a significant difference in terms of OS, DFS and TRM between patients receiving a transplant from HLA-identical sibling donors and patients receiving a transplant from either a related mismatched or an unrelated donor (P = 0.001) (Table 2). Among the 359 evaluable patients, 211 (59%) developed acute GVHD. Grade I acute GVHD was observed in 39% of cases (83 patients), grade II in 29% (61 patients), grade III in 20% (42 patients), and grade IV in 12% (25 patients). Two hundred and thirty patients were evaluable for chronic GVHD. Seventy patients (30%) developed chronic GVHD, 54% of whom had extensive disease. Post-transplant causes of deaths were related to disease progression in 39% of cases and transplant toxicity in 61% of cases. Fifty-five patients were still alive and in CR 5 years after allogeneic HSCT. Death occurred later than 5 years after transplantation in seven cases: two patients died from late relapse, three from viral infections, and two from a second malignancy.

Figure 1
figure1

Overall survival according to AML status before transplantation.

Table 2  Univariate analysis

Prognostic factors

On univariate analysis, when we considered factors over which we have no control: age 15 years, M3 subtype according to FAB classification, long first CR duration was predictive of better OS and DFS (Table 2). On the other hand, for the factors over which we have total control, we observed that the intensified conditioning regimen and T cell depletion significantly decreased the probability of OS and DFS and significantly increased TRM (Table 2). Between these two situations, we demonstrated that factors over which we have some control, such as donor type (mismatched related and matched unrelated) and acute GVHD grade II, significantly decreased OS and DFS and increased TRM (Table 2), although female donor and occurrence of chronic GVHD were associated with better OS and DFS (Table 2).

On multivariate analysis, the variables age <15 years and CR achievement before transplantation showed a favorable impact on OS (Table 3) and age <15 years was associated with lower TRM. Female donor (Figure 2), no acute GVHD or low grade acute GVHD, and chronic GVHD (Figure 3) were associated with better OS and DFS. In addition, no acute GVHD or low grade acute GVHD were associated with lower TRM. Year of transplantation, TBI-based conditioning regimens, and GVHD prophylaxis type other than T cell depletion did not show any prognostic value in terms of OS, DFS, and TRM.

Table 3  Multivariate analysis
Figure 2
figure2

Disease-free survival according to donor sex.

Figure 3
figure3

Disease-free survival according to presence or absence of chronic GVHD.

Discussion

Conventional chemotherapy appears generally unsatisfactory in advanced AML, while myeloablative therapy followed by allogeneic HSCT can produce durable remission in approximately one-third of cases.78 However, few studies reporting a large enough sample of patients to determine prognostic factors have been reported.1314151617

To our knowledge, this study is the largest cohort of patients with an advanced stage of AML undergoing allogeneic HSCT. We have shown that factors over which we have total, some, or no control can influence survival duration, risk of relapse and TRM after transplantation. Multivariate analysis pointed out the importance of factors over which we have no control (younger age, CR achievement before transplant) and factors over which we have some control (HLA-identical sibling donor, female donor, low grade acute GVHD, and chronic GVHD). These factors added substantially to the success of transplantation by increasing overall survival and by decreasing the risk of relapse and TRM.

A previous study of the International Bone Marrow Transplant Registry (IBMTR) has shown a significantly better 3-year probability of leukemia-free survival after transplantation in patients aged under 30 years and in those with a first remission duration longer than 1 year than in patients over 30 years of age and in those with a first remission lasting less than 1 year.8 In our study, we confirmed that younger patients had a better survival rate and a lower TRM. For AML patients who relapsed after conventional therapy, the place of allogeneic HSCT in untreated first relapse or in second remission is still questionable. Allogeneic HSCT in untreated first relapse has proven to be feasible in 126 patients who received transplants at the Fred Hutchinson Cancer Research Center, with a 5-year probability of relapse-free survival of 23%.18 In our current study, survival was significantly lower for patients receiving transplants in UR or in RR when compared to patients undergoing transplantation in CR. These results are quite different from those from Seattle showing no difference between patients who had transplants in untreated relapse and patients who had transplants in second or subsequent remission.19

In our series, we found better results when transplants for advanced AML were performed from HLA-identical sibling donors; transplants from unrelated donors remained disappointing. The importance of genomic typing of class I HLA alleles to the success of transplants from unrelated donors has been recently demonstrated.20 Large prospective studies, including patients with better HLA matching, would be necessary in order to determine the place of such transplants in advanced AML. Other factors over which we have some control – female donor, low grade acute GVHD, and development of chronic GVHD were associated with a lower probability of relapse after transplantation, probably corresponding to a potential graft-versus-leukemia effect. On multivariate analysis, we demonstrated the importance of factors over which we have no control (age, CR achievement) or some control (female donor, acute and chronic GVHD). Two other strategies to reduce relapse rate after allogeneic HSCT involved increasing the myeloablative function of the conditioning regimen or reducing GVHD prophylaxis before transplantation.

Intensified conditioning regimens have been tested before allogeneic HSCT in phase I–II studies.212223 A standard conditioning regimen combining TBI and cyclophosphamide with etoposide2122 or BCNU23 or busulfan13 and the combination of busulfan with melphalan14 have been examined in advanced-stage AML with encouraging results. A prospective randomized comparison of TBI-etoposide vs busulfan–cyclophosphamide did not show any difference in terms of overall survival and DFS.15 However, a statistically significant difference was observed between AML patients allografted in 2nd CR (standard risk patients) and those allografted in UR or RR (high risk patients).15 In our series, TBI and a GVHD prophylaxis type other than T cell depletion had no real impact on DFS and TRM. However, for these indications a high TRM rate, particularly in refractory and resistant patients, would suggest the need for developing new therapeutic modalities using targeted radiotherapy24 or a reduced myeloablative conditioning regimen.25

In conclusion, recommendations can be drawn from our study taking into account the outcome of treatment and prognostic factors emerging from multivariate analysis: (1) in relapsed patients, CR achievement before transplantation seems an important issue; (2) transplantation from HLA-identical sibling donors using a standard conditioning regimen and GVHD prophylaxis is recommended for patients in second or further remission; (3) unsatisfactory results of allogeneic HSCT for patients with primary refractory AML or refractory relapse require development of new HSCT modalities.

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Acknowledgements

We thank the following institutions: Hôpital Universitaire d'Angers (Angers), Hôpital Jean Minjoz (Besançon), Hôpital Haut Lévêque (Bordeaux), Höpital Universitaire de Caen (Caen), Hôpital de Percy (Clamart), Hôpital de l'Hôtel-Dieu (Clermont-Ferrand), Hôpital Henri Mondor (Créteil), Hôpital de Dijon (Dijon), Hôpital Michallon (Grenoble), Hôpital Huriez (Lille), Hôpital Debrousse (Lyon), Institut Paoli-Calmettes (Marseille), Hôpital Lapeyronie (Montpellier), Hôpital de Brabois (Nancy), Hôpital de l'Hôtel-Dieu (Nantes), Hôpital de l'Archet (Nice), Hôpital Cochin (Paris), Hôpital Hôtel-Dieu (Paris), Hôpital Necker Adultes (Paris), Hôpital Necker Enfants (Paris), Hôpital de la Pitié Salpêtrière (Paris), Hôpital Saint Louis (Paris), Institut Gustave Roussy (Paris), Hôpital Jean Bernard (Poitiers), Hôpital de Pontchaillon (Rennes), Hôpital Becquerel (Rouen), Hôpital Charles Nicolle (Rouen), Hôpital Nord (Saint-Etienne), Hôpital de Hautepierre (Strasbourg), Hôpital de Purpan (Toulouse), Hôpital Paul Brousse (Villejuif).

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Correspondence to M Michallet.

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Keywords

  • allogeneic
  • HSCT
  • advanced
  • AML

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