Although allogeneic hematopoietic stem cell transplantation (HSCT) is considered the only curative treatment for refractory or relapsed follicular lymphoma (FL), transplant-related mortality (TRM) greatly interferes with the success. A variety of reduced-intensity conditionings (RICs) have been used to reduce TRM, but an optimal conditioning for FL has not been fully established. We retrospectively evaluated the outcome of allogeneic HSCT for FL with RIC consisting of fludarabine and melphalan. Nineteen adult patients with relapsed or refractory FL were conditioned with fludarabine (125 mg/m2) and melphalan (140 mg/m2), and received grafts from an HLA-identical sibling (n = 6) or an unrelated donor (n = 13). For the prophylaxis of graft-versus-host disease (GVHD), cyclosporine A or tacrolimus with short-term methotrexate was given. There were no early deaths before engraftment, and all patients achieved engraftment. Three patients died of extensive-type chronic GVHD (n = 2) or bacterial infection (n = 1) without disease progression. With a median follow-up period of 75.2 months (range: 33.3–111.9 months), 16 patients were alive without disease progression. Both the 5-year overall and progression-free survival rates were 84.2% (95% CI: 67.7–100%). These results strongly suggest that allogeneic HSCT with RIC using fludarabine and melphalan could be a promising treatment choice for refractory or relapsed FL.
Current chemotherapies, such as rituximab-containing regimens, have improved the prognosis of follicular lymphoma (FL). However, FL is generally considered incurable with these conventional treatments, and the disease relapses in most patients . High-dose chemotherapy with autologous or allogeneic hematopoietic stem cell transplantation (HSCT) has been shown to improve the survival rates of relapsed or refractory FL [2, 3]. When compared with autologous HSCT, a significant reduction in relapse rate has been observed after allogeneic HSCT with myeloablative conditioning [4–6]. The suggested mechanism of the reduced relapse rate is the graft-versus-lymphoma (GVL) effect provided by transplanted donor cells. However, this favorable effect is often offset by the high transplant-related mortality (TRM) of allogeneic HSCT following myeloablative conditioning. To reduce TRM, most of the recent studies have focused on the use of reduced-intensity conditioning (RIC). The outcomes are promising and the practice of allogeneic HSCT has shifted in favor of RIC, although registry data showed an increased risk of late disease progression after RIC regimens [7, 8]. The definition of RIC included a variety of regimens which varied significantly in their intensity and immunosuppressive effects. Thus, the optimal RIC regimens of allogeneic HSCT for FL have yet to be established, and long-term follow-up is also lacking in most of the earlier studies. Therefore, we retrospectively evaluated the long-term outcome of allogeneic HSCT with RIC consisting of fludarabine and melphalan for relapsed or refractory FL.
Nineteen patients with histologically proven FL without transformation who underwent allogeneic HSCT at Keio University Hospital (Tokyo, Japan) between June 2002 and January 2009 after being conditioned with fludarabine and melphalan were evaluated. No patients received anti-thymocyte globulin (ATG) as part of the conditioning regimen. The patient and transplant characteristics are shown in Table I. None of the patients were in complete remission (CR) at the time of transplant. Most of the patients had received multiple lines of chemotherapy; two had received autologous and two had received allogeneic HSCT. In the two patients who had undergone allogeneic HSCT, the graft was rejected along with the recovery of autologous hematopoiesis after conditioning with fludarabine and cyclophosphamide. Both patients experienced disease progression thereafter and decided to undergo the second allogeneic HSCT from the same HLA-identical sibling and a different HLA-matched unrelated donor, respectively. Thirteen patients received stem cells from an unrelated donor.
|Median age (range)||47 (34–58)|
|Disease status at transplant|
|No. of lines of prior chemotherapy|
|3 or less||12|
|4 or 5||5|
|6 or more||2|
|Allograft (graft rejection)||2|
|Stem cell donor|
|Related (BM/PBSC)||6 (4/2)|
|CsA and methotrexate||6|
|Tacrolimus and methotrexate||13|
In all 19 patients, engraftment was achieved at a median of 19 (range, 13–25) days after transplantation, and full donor chimerism was also confirmed within 28 day after transplantation. No patients received donor lymphocyte infusion (DLI). Incidences of acute GVHD were Grade 0–1 in 10 (53%), Grade 2 in 8 (42%), and Grade 3 in 1 patient (5%). The patient who developed Grade 3 acute GVHD received peripheral blood stem cells from an HLA-identical sibling donor. Cumulative incidence of any type of chronic GVHD was 61.1% (95% CI: 38.6–83.6%).
The transplant procedure was generally well-tolerated. Grade 3 or greater organ toxicities consisted of oral mucositis (n = 4), diarrhea (n = 7), hepatotoxicity (n = 7), and nephrotoxicity (n = 1). All these toxicities were reversible and manageable with supportive care. No patients developed hepatic veno-occlusive disease/sinusoidal obstruction syndrome. Post-transplant infectious complications were cytomegalovirus (CMV) infection (n = 8), CMV gastrointestinal diseases (n = 3), viral hemorrhagic cystitis (n = 6), and bacterial infection (bacteremia: n = 4; pneumonia: n = 2; enterocolitis: n = 1). The follow-up period of the 16 patients who were alive at the time of analysis ranged from 33.3 to 111.9 months with a median of 75.2 months. There were three cases of TRM, and the causes were bacterial infection (bacteremia; n = 1) and extensive-type chronic GVHD involving the gastrointestinal tract (n = 1) or liver (n = 1). One patient who developed fatal bacteremia due to Escherichia coli had a 7-year history of chemotherapy for FL and developed Grade 3 mucositis after transplantation. No patients showed disease relapse or progression, and thus the 5-year overall survival (OS) and progression free survival (PFS) rates were both 84.2% (95% CI: 67.7–100%; Fig. 1). All surviving patients had an Eastern Cooperative Oncology Group (ECOG) performance status of 0 (n = 14) or 1 (n = 2), and none of the patients were receiving immunosuppressive therapy at the time of analysis. There was no case of secondary cancer during the follow-up.
The results of this study suggest that RIC consisting of fludarabine and melphalan offers promise as a conditioning regimen for patients with relapsed or refractory FL undergoing allogeneic HSCT by providing a high PFS rate (84%) with a low TRM. The most notable finding was that disease progression was not observed in any of the patients even with a long-term follow-up (median 75 months). In contrast to other studies including relatively high proportion (20–60%) of patients in CR [7–13], no patients in CR were included in our cohort. However, our results were comparable to or more favorable than those of the studies showing the PFS rates ranging between 32% and 84%. In these studies, the RIC regimens used for FL were quite variable, and included fludarabine-based regimens in which fludarabine was combined with cyclophosphamide, low-dose TBI, busulfan or melphalan, and BEAM. Khouri et al.  reported a favorable outcome by using fludarabine and cyclophosphamide in combination with pre- and post-transplant rituximab . In addition, some of these RIC regimens were incorporated with alemtuzumab or ATG for in-vivo T-cell depletion. The degrees of anti-lymphoma effects, myelosuppression, immunosuppression, and organ toxicity vary significantly among these RIC regimens, making it difficult to compare the results of allogeneic HSCT using different RIC regimens for FL. The combination of fludarabine and melphalan used in this study achieved full donor chimerism shortly after transplantation without DLI, and disease progression was not observed in any of the patients, suggesting its considerable immunosuppressive effect and intensive anti-leukemia/lymphoma effect . Since DLI required for the conversion to full donor chimerism has the potential to cause serious GVHD, this regimen can be a good candidate for the conditioning regimen in this setting.
In this study, CSA or tacrolimus with short-term methotrexate was used for the prophylaxis of GVHD. It is notable that the incidence of severe acute GVHD was low among the two thirds of patients receiving HSCT from unrelated donors, which could partly explained by the use of tacrolimus for the prophylaxis of GVHD for HSCT from unrelated donors and the ethnic background [15–18]. In contrast, more than half of evaluable patients developed extensive-type chronic GVHD, and accounted for two of the three deaths observed in this study. There is a possibility of increase in disease relapse using highly intensive immunosuppressive therapies such as in vivo or in vitro T-cell depletion to prevent GVHD. However, FL has been shown to be highly sensitive to the GVL effect .Therefore, more intensive immunosuppression could improve the survival by decreasing severe life-threatening GVHD. The use of ATG could be an option, since it has been reported that a conditioning regimens including ATG could decrease the incidence of extensive-type chronic GVHD . While maintaining a balance with the anti-lymphoma effects of fuldarabine plus melphalan, future studies should focus on optimizing the prophylaxis and treatment of GVHD.
In conclusion, allogeneic HSCT following RIC consisting of fludarabine and melphalan could be a promising conditioning regimen for refractory or relapsed FL with adequate supportive care. Future studies will be needed to optimize the post-transplant immunosuppression in this setting.