Autologous hematopoietic stem cell transplantation for relapsed follicular lymphoma: safety profile and clinical outcome in a single-center experience

Follicular lymphoma (FL) is a B-cell malignancy with an indolent clinical course and characterized by lymphadenopathy, splenomegaly and bone marrow involvement. Most patients are over 60 years at diagnosis and were found to have t(14;18), resulting in the overexpression of bcl-2 protein which is involved in apoptosis [1]. Most asymptomatic FL patients at early disease stage do not require treatment [2], whereas those with symptomatic and advanced-stage disease receive chemotherapy plus rituximab [3]. The value of autologous hematopoietic stem cell transplantation (AHSCT) as a first remission consolidation is to be established as the vast majority of studies were performed in the pre-rituximab era. In sum, the benefits were demonstrated in terms of progression-free survival (PFS), but not in overall survival (OS) [4]. A large number of studies have shown some benefits of AHSCT in R/R FL, but they have been conducted prior to the widespread use of rituximab [5, 6]. Nevertheless, AHSCT for R/R FL remains controversial and to date the evidence-based data are lacking. The current indications for AHSCT in R/R FL setting have been recently proposed by expert panel of EBMT-Lymphoma Working Party. The inclusion criteria for AHSCT in RR F/R are as follows: patients in first and subsequent chemo-sensitive relapse, especially those with a short duration of response to immuno-chemotherapy and high FLIPI score [7].

Herein, we present the results of our 30 patients with relapsed/recurrent FL who were performed AHSCT in our center.

Autologous hematopoietic stem cell transplantation can yield long-term disease-free survival when performed for FL after relapse, and this seems to be true for both patients treated in the pre-rituximab era and at the time of its wide availability [9]. However, most studies on the results of AHSCT for FL have been reported for patients who did not obtain rituximab in their induction therapy. Of note is that the vast majority of studied patients received total body radiotherapy containing regimen as a high-dose therapy. The OS and PFS at 10 years were 50 and 28 %, respectively, with ~20 % of patients being in CR 18 years after AHSCT [10]. One of the largest nonrandomized studies reported on the results of AHSCT for 248 recurrent FL patients. The preparative regimen consisted of chemotherapy in 60 % of patients, and the remaining 40 % received radiotherapy. The 5-year OS and PFS were 63 and 44 %, respectively [11]. It should be emphasized that despite the small number of included patients to our study, the OS and PFS rates were comparable with those obtained by other groups [10‐12].

The significant advantage of AHSCT over standard chemotherapy for R/R FL has been unquestionably determined in the only randomized study to date. The 5-year PFS was 10 % in chemotherapy arm versus 55 % in the transplant arm; there was also a significant benefit in terms of OS in the latter one [6].

The addition of rituximab to conventional chemotherapy in FL has improved outcome; however, the plateau on PFS curves was not demonstrated [13]. Conversely, AHSCT for relapsed FL may lead to eradication of a malignant clone in a certain proportion of patients. Namely, the plateau on the PFS curve was 50 % at 7.5 years [14]. In contrast, no plateau was demonstrated by other reports [15] including ours.

It was also found that the use of AHSCT in first relapse of FL regardless of prior exposure to rituximab has ameliorated the 3-year OS [16]. A large prospective and randomized study has been recently conducted to investigate the efficacy of rituximab used both as in vivo purging before AHSCT and as posttransplant maintenance. Median follow-up of 280 enrolled FL patients was 8.3 years. There was no difference in 10-year PFS and OS between rituximab and no rituximab arms in terms of pre-AHSCT purging. The addition of rituximab as a maintenance treatment after AHSCT has significantly prolonged PFS, but no OS if compared with observation arm [17]. It remains unclear whether there is a benefit of AHSCT for R/R FL patients who received prior chemotherapy with rituximab as a first-line therapy. The incorporation of rituximab into the transplant procedure may decrease the risk of relapse via deeper reducing of tumor burden before AHSCT [11]. The encouraging results were obtained for R/R FL patients who were treated with immuno-chemotherapy and in vivo purging before AHSCT with the 5-year PFS of 59 % [18].

Nevertheless, it was demonstrated that 3-year PFS after AHSCT for rituximab-naïve and rituximab-treated FL patients was comparable (72 vs. 75 %, respectively). The 3-year OS rates were 92 % for both arms. A trend for better 3-year PFS rate after AHSCT was found for rituximab-naïve patients receiving rituximab at progression versus those who did not receive rituximab at relapse (p = 0.07). AHSCT was beneficial in terms of PFS and OS for rituximab-treated FL patients if compared with those not receiving transplantation (p = 0.052) [16]. To date, there are no prospective studies that demonstrated the superiority of AHSCT over conventional chemotherapy in the rituximab era. Some single studies have shown a better disease control in AHSCT arm, but it did not translate into better OS [19]. It may be partially due to an increased risk of secondary cancers after autograft [16]; however, this presumption has not been shown by others [20], including us. It was concluded that radiotherapy as a preparative regimen before AHSCT might be responsible for the development of secondary malignancies and should be avoided [12]. In our study, radiotherapy was not a part of conditioning and no patient with secondary malignancy was detected after maximum of more than 18 years of follow-up. ⁹⁰Y-radiolabeled ibritumomab tiuxetan was administered before AHSCT in five patients, and it was well tolerated. As the number of treated patients was low, it is difficult to draw far-reaching conclusions. Nevertheless, three out of the five treated patients are free of disease at the last contact.

In a majority of patients, the toxicity of transplant procedure was manageable and only one early posttransplant death due to severe pulmonary infection was observed in our study group. TRM at 100 days was 3 %. This finding is in line with the TRM rates provided by other groups [15, 21]. There was no difference in the PFS and OS rates regardless of FLIPI score and disease status at transplant. The similar results have been demonstrated by other groups [14]. Nevertheless, the following adverse risk factors for predicting a worse OS were identified: grade 3 FL, high FLIPI index at transplant and 3 or more chemotherapy lines before AHSCT [11]. This finding, however, requires confirmation in other studies.

AHSCT for relapsed FL pretreated with rituximab remains a safe procedure with low TRM and long-term progression-free survival in about one-third of transplanted patients with no plateau. It seems reasonable to offer AHSCT for relapsed FL patients; however, its utility in the rituximab era requires to be elucidated.