Abstract
Post-transplantation lymphoproliferative disorders (PTLD) are the second most frequent malignancies after solid organ transplantation and cover a wide spectrum ranging from polyclonal early lesions to monomorphic lymphoma. Available treatment modalities include immunosuppression reduction, immunotherapy with anti-B-cell monoclonal antibodies, chemotherapy, antiviral therapy, cytotoxic T-cell therapy as well as surgery and irradiation. Owing to the small number of cases and the heterogeneity of PTLD, current treatment strategies are mostly based on case reports and small, often retrospective studies. Moreover, many studies on the treatment of PTLD have involved a combination of different treatment options, complicating the evaluation of individual treatment components. However, there has been significant progress over the last few years. Three prospective phase II trials on the efficacy of rituximab monotherapy have shown significant complete remission rates without any relevant toxicity. A prospective, multicenter, international phase II trial evaluating sequential treatment with rituximab and CHOP-based chemotherapy (cyclophosphamide, doxorubicin, vincristine, prednisone) is ongoing and preliminary results have been promising. Cytotoxic T-cell therapy targeting Epstein–Barr virus (EBV)-infected B cells has shown low toxicity and high efficacy in a phase II trial and will be a future therapeutic option at specialized centers. Here, we review the currently available data on the different treatment modalities with a focus on PTLD following solid organ transplantation in adult patients.
Keywords
Introduction
Post-transplant lymphoproliferative disorders (PTLD) are the second most common neoplastic diseases following solid organ transplantation (SOT) [Penn et al. 1969]. The clinical presentations of PTLD are diverse and differentiating between PTLD and infectious complications in the post-transplant period is challenging. In children who have a primary Epstein–Barr virus (EBV) infection after organ transplantation, the manifestations of PTLD often resemble those of systemic mononucleosis, with B symptoms and lymphadenopathy most prominently affecting Waldeyer’s ring and the cervical lymph nodes. In adults, more than 70% of SOT recipients have extranodal manifestations and findings associated with PTLD are often discovered incidentally in asymptomatic patients undergoing routine post-transplantation follow-up examinations. The extranodal sites most frequently affected by PTLD are liver (30–40%), gastrointestinal tract (20–25%), lungs (15–20%), kidneys (10–15%) and central nervous system (10%). The transplanted organ shows PTLD infiltration in 15–20% of patients. There are two peaks in the incidence of PTLD after organ transplantation. The earlier peak is in the first 12 months after transplantation (early PTLD); half of all cases of PTLD occur during this interval, with a median manifestation time of 6 months after transplantation. A second incidence peak appears 5–10 years after transplantation (late PTLD).
Most cases of PTLD are B-cell lymphomas; up to 5% are T-cell lymphomas, Hodgkin, or Hodgkin-like lymphomas. These aspects of PTLD are reflected in the WHO classification of PTLD, as outlined in Table 1 [Swerdlow et al. 2008]. PTLD staging is analogous to the Ann Arbor classification. Most patients are diagnosed with PTLD in an advanced stage (III/IV).
WHO classification of PTLD.
PTLD, post-transplantation lymphoproliferative disorders.
Two aspects of PTLD pathophysiology have a direct impact on treatment: immunosuppression and EBV infection. The key role of immunosuppression is evident from epidemiological data: the lifetime risk of developing PTLD depends on the transplanted organ and is 1–2% after kidney transplantation [Shahinian et al. 2003; Dharnidharka et al. 2001; Libertiny et al. 2001], 5–6% after heart, heart/lung and lung transplantation [Katz et al. 2007; Webber et al. 2006; Gao et al. 2003; Reams et al. 2003; Ramalingam et al. 2002; Paranjothi et al. 2001] and 2–10% after liver transplantation [Kremers et al. 2006; Vallejo et al. 2005; Duvoux et al. 2002; Jain et al. 2002; Lemoine et al. 2001; Wu et al. 2001; Glez-Chamorro et al. 2000; Zein et al. 2000; Pageaux et al. 1998], correlating with the intensity of immunosuppression. Furthermore, rejection crises necessitating intensified immunosuppression and high-dose cyclosporine A protocols increase the risk for the development of PTLD [Gao et al. 2003]. The type of immunosuppression also appears to have some influence, as use of mycophenolate mofetil (MMF) after renal transplantation seems to be associated with a lower incidence of PTLD [Birkeland and Hamilton-Dutoit, 2003].
EBV, a ubiquitous lymphotropic and epitheliotropic γ1-herpesvirus, is detectable in lesions of PTLD in about 50% of cases [Trappe et al. 2009a; Choquet et al. 2006; Oertel et al. 2005] and is believed to be one of the major factors involved in the pathogenesis of PTLD [Young et al. 1989]. More than 90% of the adult population worldwide is infected with EBV [Fleisher et al. 1979]. Primary EBV infection is highly immunogenic and leads to a massive expansion of virus-specific and nonspecific T cells with subsequent elimination of the EBV-infected B cells. A small number of the EBV-infected B cells, however, escape this immune response by producing just a single viral protein (latent infection). In immunocompetent individuals, equilibrium is reached between latently EBV-infected B cells and the cellular immune response. In immunocompromised individuals on the other hand, there is a higher degree of viral replication and the peripheral blood contains a greater number of latently EBV-infected B lymphocytes [Babcock et al. 1999], which EBV continually stimulates to proliferate. Viral proteins such as the EBV-specific ‘latent membrane protein 1’ (LMP1) act directly on cellular mechanisms of growth regulation and induce hyperproliferation [Liebowitz, 1998]. The inadequately controlled B-cell proliferation stimulated by EBV infection is believed to lead to PTLD. In the histological subgroup of so-called ‘early lesions’ (about 5% of all cases of PTLD), nearly all cells are infected with EBV, and the lesions are polyclonal. In the biologically more advanced polymorphic and monomorphic types of PTLD (making up 15–20% and >70% of all cases of PTLD, respectively), EBV-positive and EBV-negative B cells can be found adjacent to one another. Polymorphic PTLD is mainly polyclonal or oligoclonal, while monomorphic PTLD is frequently monoclonal and, in as many as 50% of all cases, EBV negative as well. Thus, EBV seems to be an essential factor for the pathogenesis of PTLD in its early phase; in later phases, however, EBV appears not to be needed any more for the growth and survival of lymphoma cells. Nearly 60% of all EBV-naive transplant recipients (some 90% of adult organ recipients are already serologically EBV-positive before transplantation), will develop a primary EBV infection of which 50% will be asymptomatic, 25% will resemble infectious mononucleosis and the remaining 25% will present as PTLD [Smith et al. 2007]. This symptomatic condition corresponds to the early phase of PTLD before it becomes overt; it seems to be due to the patient’s inability to mount a full immune response to EBV because of immunosuppressive therapy. The transplantation of an EBV-positive donor organ (as is true in the vast majority of cases) into an EBV-negative recipient (D+R-) is therefore considered a high-risk situation.
There is still some debate as to whether EBV load in the peripheral blood of transplant patients predicts onset of PTLD or relapse following treatment and which therapeutic consequence should result from an elevated EBV load. Very briefly, our view is that individual EBV load in adult PTLD patients during long-term follow up does not correlate with treatment response and therefore is not suitable as a predictive marker for effective therapy or PTLD relapse in adult patients after prior use of rituximab, although it may be useful to detect patients at risk for PTLD [Scheenstra et al. 2004; Yancoski et al. 2004; Fellner et al. 2003; Orentas et al. 2003; Wagner et al. 2002; Rowe et al. 2001, 1997; Yang et al. 2000; Vajro et al. 2000; Kogan et al. 1999; Green et al. 1998; Kenagy et al. 1995; Riddler et al. 1994].
Treatment of PTLD
Owing to the small number of cases and the heterogeneity of PTLD, current treatment strategies are mostly based on case reports, and small, generally retrospective studies. Moreover, many studies on the treatment of PTLD have involved a combination of different treatment options (such as immunosuppression reduction, antiviral therapy, monoclonal antibodies and chemotherapy), complicating the evaluation of individual treatment components. Thus, no generally accepted treatment strategy for PTLD has become established to date. Information from prospective, interventional phase II trials is available only for treatment of CD20-positive B-cell PTLD with the anti-CD20 antibody rituximab and for sequential treatment with rituximab followed by CHOP (cyclophosphamide, doxorubicin, vincristine, prednisone) or R-CHOP (Rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone) chemotherapy. For CD20-negative PTLD, CHOP-based chemotherapy is used most frequently, while other chemotherapeutic strategies, antivirals and immunomodulatory therapy [interferon (IFN)-alpha, interleukin (IL)-6 antibodies, intravenous immunoglobulin (IVIg), EBV-specific T-cell therapy] are usually reserved for rare PTLD subtypes, PTLD in the context of primary EBV infection and relapsed or refractory disease.
About 70–80% of adults with PTLD are diagnosed at an advanced stage of the disease. Diffuse large B-cell lymphoma (DLBCL) is the most common histological finding [Trappe et al. 2009a; Choquet et al. 2006; Oertel et al. 2005]. Here, chemotherapy or immunotherapy must be considered as a primary treatment option. However, infectious complications after chemotherapy are far more common in transplant recipients than in the nontransplant population due to longstanding immunosuppression. Anti-CD20 monotherapies are not associated with clinically relevant infectious toxicity. However, they seem to be less effective than chemotherapy [Choquet et al. 2007a].
Immunosuppression reduction
Initial therapeutic action at diagnosis of PTLD is immunosuppression reduction (IR), often effective in patients with early, polymorphic PTLD, particularly in children after primary EBV infection. In the first retrospective study, all 17 patients treated by immunosuppression reduction responded, but all 17 also went on to lose the transplanted organ [Starzl et al. 1984]. A recent retrospective analysis of 62 adult patients treated with IR alone over a 20-year period demonstrated a response rate [complete remission (CR) and partial remission (PR)] of 45% [Reshef et al. 2011]. These response rates seem high in the light of our own clinical experience and may be due to the high proportion of patients with polymorphic PTLD (37%) and early disease stage (52%). Of note, the incidence of acute allograft rejection in this group of patients was 40%. In contrast, in our experience with patients treated with IR + chemotherapy ± rituximab for PTLD after renal transplantation, we found a noninferior graft function compared with untreated controls, suggesting that the negative impact of IR on graft function can be fully compensated by the immunosuppressive effect of chemotherapy [Trappe et al. 2009b]. In monomorphic PTLD, significant clinical response to IR can be expected in only about 10% of patients [Allen et al. 2001; Tsai et al. 2001; Swinnen, 2000] and it is neither possible nor advisable to wait for a response to IR. Nevertheless, as IR is used in the vast majority of published studies, it is difficult to eliminate a possible benefit and IR remains standard treatment in PTLD.
CHOP-like chemotherapy
Several retrospective studies have evaluated CHOP-like chemotherapy in PTLD [Choquet et al. 2007a, 2007b; Elstrom et al. 2006; Fohrer et al. 2006; Taylor et al. 2006; Norin et al. 2004; Mamzer-Bruneel et al. 2000; Garrett et al. 1993] (for a summary, see Table 2). Common problems include small patient cohorts, retrospective format, a broad spectrum of different PTLD subtypes, variable front-line therapy including IR, rituximab and antiviral therapy as well as heterogeneous chemotherapy regimens. In the retrospective analysis from our own study group (median follow up 8.8 years), first-line CHOP demonstrated a complete response rate of 50% (overall response rate [ORR] 65%) and median overall survival of 13.9 months in 26 patients not responding to IR [Choquet et al. 2007b]. Treatment-related mortality was 31%, primarily from infections complications, and PTLD-associated mortality rates were 15%, 31% and 38% at 1, 5 and 10 years, respectively. Taken together, the available data indicate that CHOP chemotherapy offers a potential for cure of PTLD but is associated with substantial toxicity and mortality, making prophylactic use of granulocyte colony stimulating factor (GCSF) and antibiotics mandatory.
Studies of first-line CHOP or CHOP-like chemotherapy in adult PTLD.
PTLD, post-transplantation lymphoproliferative disorders; IR, immunosuppression reduction; CR, complete remission; PR, partial remission; OS, overall survival, R-CHOP, rituximab + CHOP chemotherapy (cyclophosphamide, doxorubicin, vincristine, prednisone); ACVBP, doxorubicin, cyclophosphamide, vindesine, bleomycin, prednisone; ORR, overall response rate; TRM, therapy-associated mortality; PMitCEBO, prednisolone, mitoxantrone, cyclophosphamide, etoposide, bleomycin, vincristine.
#Patients with initial cerebral involvement.
PACEBOM (prednisone, doxorubicin, cyclophosphamide, etoposide, bleomycin, vincristine, methotrexate), ChlVPP PABlOE (doxorubicin, bleomycin, vincristine, etoposide alternating with chlorambucil, vinblastine, procarbazine, prednisone), CHOD/BVAM (cyclophosphamide, doxorubicin, BCNU, vincristine, methotrexate, cytosine arabinoside).
Rituximab monotherapy
The introduction of single-agent rituximab has markedly changed PTLD management. In two independently performed, large, multicenter, prospective phase II trials, rituximab monotherapy was administered at a dose of 375 mg/m2 weekly for four consecutive weeks. One demonstrated complete remission in 9 of 17 patients (52%) [Oertel et al. 2005], while the other showed a 44% response rate and a 28% rate of complete remission in 43 patients [Choquet et al. 2006]. A combined analysis of both studies [Choquet et al. 2007a] demonstrated that 30/60 patients (50%) had experienced disease progression 6 months after completion of rituximab therapy, and 34/60 (57%) at 12 months. Of the 35/60 patients who initially responded, 9 (26%) progressed within the first year following therapy (4/25 CR, 5/10 PR). At a median follow up of 16.3 months, median progression-free survival (PFS) was 6.0 months (95% CI 1.8–10.1 months). However, of the 34 patients who progressed after first-line treatment with single-agent rituximab, 32 received further treatment: rituximab monotherapy in 5 patients (1 PR, 1 stable disease [SD], 3 progressive disease [PD]), chemotherapy (mainly CHOP) in 26 (11 CR, 2 PR, 4 SD, 7 PD) and irradiation with further IR in one patient, who achieved CR. Finally, median overall survival was 34.5 months, with 1- and 2-year overall survival rates of 72.5% and 51.8%. A retrospective analysis identified risk factors (age, serum lactate dehydrogenase [LDH], performance status) and a high-risk group of patients who all required subsequent chemotherapy.
Treatment with extended doses of rituximab adapted to response was another approach evaluated in a prospective, multicenter, phase II rituximab monotherapy trial from Spain [Gonzalez-Barca et al. 2007]. Patients were treated with IR and 4-weekly infusions of rituximab. Those patients who did not achieve CR received a second course of four rituximab infusions. After the first course of rituximab, 13/38 (34%) patients achieved CR. Of 17 patients achieving PR, 12 could be treated with a second course of rituximab, and 10/12 achieved CR, yielding an intention-to-treat CR rate of 61%. Event-free survival in this study was 42% and overall survival was 47% at 27.5 months, similar to the results achieved after four courses of rituximab [Choquet et al. 2007a]. In conclusion, single-agent rituximab as first-line treatment after IR is an effective and rational treatment approach, but may be suboptimal for intermediate and high-risk patients. In contrast to chemotherapy, there is virtually no clinically relevant infectious toxicity. Extended doses of rituximab may increase the CR rate, but whether this translates into an improved overall survival is unknown.
A recent retrospective analysis of 80 adult patients treated for PTLD at four Chicago institutions between 1998 and 2008 indicated that a selection for low-risk patients can increase the response rates to rituximab monotherapy [Evens et al. 2010]. Rituximab monotherapy was identified as the chosen treatment in 26/80 (33%) of patients. Another 33/80 (41%) had been treated with rituximab plus chemotherapy and 21/80 had received treatment not including rituximab. Patients treated with rituximab monotherapy had a lower International Prognostic Index (IPI 3–5 36% versus 64%) and less-frequent bulky disease (17% versus 68%) compared with those treated with rituximab plus chemotherapy. In this low-risk group, 20 of 26 (76%) were reported to be alive without evidence of disease after rituximab monotherapy. For a summary of results with rituximab monotherapy in PTLD, see Table 3.
Prospective studies of first-line rituximab monotherapy in adult PTLD.
PTLD, post-transplantation lymphoproliferative disorders; IR, immunosuppression reduction; CR, complete remission; PR, partial remission; ORR, overall response rate; TRM, therapy-associated mortality.
Sequential treatment with rituximab and CHOP-21 chemotherapy + GCSF
In 2003, the European Study Groups on PTLD started a cooperative, multicenter, prospective, phase II trial to investigate the efficacy and safety of sequential treatment with rituximab and CHOP-21 in PTLD unresponsive to immunosuppression reduction. The extent and duration of upfront IR was at the discretion of the treating physician, but usually calcineurin inhibitors were reduced by 30–50% while azathioprine or MMF was stopped. For study inclusion, patients were required to have failed to respond significantly to an upfront reduction of immunosuppression, defined as disease with a clinical impact at 2 weeks after IR. Within the study patients were treated sequentially with rituximab followed by four cycles of CHOP + GCSF starting 4 weeks after the last dose of rituximab (Figure 1). An interim analysis was presented at the December Meeting of the American Hematology Society (ASH) in 2009 after 64 patients had finished the protocol [Trappe et al. 2009a]. Sixty one patients had been diagnosed with monomorphic PTLD, 3 with polymorphic PTLD. Most patients with monomorphic PTLD showed an aggressive histology (48 DLBCL-type, 2 Burkitt). Twenty seven patients were kidney, 15 liver, 13 heart, 6 heart/lung or lung and 3 kidney + pancreas transplant recipients. The overall response rate of sequential therapy was 89% with 69% of patients achieving a CR. CHOP was effective in nonresponders to rituximab and more than half of patients with PD after rituximab monotherapy pretreatment reached PR or even CR after CHOP. A total of 86%, 75% and 75% of patients were without disease progression at 1, 2 and 3 years, respectively. Disease-free survival was 87%, 78% and 70% at 1, 2 and 3 years. There were 6 early treatment-associated deaths (9%) resulting from infections and 2/64 patients died from refractory PTLD. Two further patients died due to hemorrhage during treatment. With 64 patients analyzed, this was the largest prospective trial in PTLD presented so far. Sequential treatment with rituximab and CHOP seems to be less toxic than and at least equally as effective as CHOP first-line treatment, while the rate of CR is higher and PFS is longer compared with rituximab monotherapy. In consequence, sequential treatment with rituximab and CHOP was considered the standard of care for CD20-positive B-cell PTLD unresponsive to IR at the ASH meeting in 2009.
Sequential treatment (ST) and risk-stratified sequential treatment (RSST) with rituximab and CHOP: Treatment algorithms in the European PTLD-1 trial. CR, complete remission; SD, stable disease; PR, partial remission; PD, progressive disease. *risk stratification according to results of restaging.
Risk-adapted sequential treatment
An earlier interim analysis of the PTLD-1 trial in 2007 had demonstrated that treatment response to rituximab (CR/PR versus SD/PD) evaluated directly before patients received CHOP chemotherapy was a significant predictor of overall survival (91.3% vs. 56.5% at 1 year, p = 0.0107) [Trappe et al. 2007a]. In order to further improve safety and efficacy in PTLD therapy, risk stratification was introduced according to the patients’ response to rituximab treatment. Patients who achieved a CR after four applications of rituximab carried on with four additional applications of rituximab at 3-week intervals while all others received R-CHOP-21 + CSF instead of CHOP-21 + GCSF (risk-stratified sequential treatment [RSST]; see Figure 1). Synergistic effects of rituximab and CHOP were retained in this very high-risk group. First results from this ongoing trial were also presented at the December Meeting of the ASH in 2009 after recruitment of 40 patients [Trappe et al. 2009a] and showed an ORR of 90% (73% CR). A total of 90% of patients were without disease progression at 1 year, while there was one early treatment-related death due to infection (2.5%). Introduction of risk stratification according to the response to four courses of rituximab monotherapy might further improve treatment results by restricting chemotherapy-related toxicity to high-risk patients. However, a longer follow up is needed.
Therapy of PTLD unresponsive to or relapsing after upfront cytotoxic therapy
Salvage therapy in relapsed PTLD after cytotoxic therapy is challenging. Intensified salvage regimens are rarely feasible due to immunosuppressive conditions and potential organ (especially kidney and bone marrow) malfunction. However, reduced intensity chemotherapy and rituximab monotherapy can induce a second remission and even cure patients. Alternative options include antiviral therapy or more experimental approaches such as IFN-alpha, EBV-specific T-cell therapy, anti IL-6 antibodies and/or administration of immunoglobulins.
Rituximab (re)treatment
With respect to the high toxicity of salvage chemotherapy in PTLD, single-agent rituximab (re)treatment was evaluated as a less-toxic alternative to chemotherapy in adult SOT recipients with a second progression of PTLD after upfront chemotherapy with or without rituximab [Trappe et al. 2007c]. Eight patients (7 adults, 1 child) were included in this retrospective study. Three of the seven adults achieved CR while one achieved PR and one SD. The median PFS for all patients after salvage therapy with single-agent rituximab was 9 months. The median OS of patients after diagnosis of PTLD was 77 months. There was no relevant therapy-associated toxicity in any of the patients. Therefore, single-agent rituximab salvage therapy is a feasible treatment approach even in patients that had previously been treated with rituximab-containing immunochemotherapy and may be useful in patients with PTLD in a multimodal treatment approach by making it possible to re-induce remission at a low toxicity level. However, response to upfront chemotherapy may influence response to subsequent salvage therapies as a response to rituximab salvage therapy has so far been described in patients with relapsing but not refractory PTLD.
Options for salvage chemotherapy
As shown above in our discussion of sequential treatment, CHOP chemotherapy is a rational choice in patients refractory to or relapsing after rituximab monotherapy. This had previously been evaluated in a retrospective analysis of 11 patients who had received IR and single-agent rituximab as a first-line treatment [Trappe et al. 2007b].
Data for treatment of PTLD refractory to CHOP chemotherapy, however, is more limited. A pilot study assessed the feasibility and efficacy of carboplatin and etoposide (CE) chemotherapy + GCSF in patients with PTLD after SOT refractory or relapsing after CHOP-based chemotherapy [Oertel et al. 2003]. Therapy consisted of carboplatin (area under the curve [AUC] 4) on day 1, etoposide (120 mg/m2) on days 1–3 and GCSF starting on day 5 every 21 days. Nine patients (seven with refractory, two with relapsed disease) were enrolled. Five patients were heart transplant recipients, three liver transplant recipients and one patient had had a double lung transplant. Overall, five patients achieved a complete remission, with follow up at 92, 39, >55, 17 and >9 months. One patient showed SD after two cycles of CE and one patient had PD. There were two treatment-related deaths. Considering the difficulties encountered in treating patients with PTLD refractory to CHOP, the combination of carboplatin and etoposide with GCSF support proved to be an effective regimen. In the future, however, this regime will probably be less effective in patients pretreated with R-CHOP than it has been historically after CHOP, an effect that has been noted in salvage therapy for non-transplant-related DLBCL [Gisselbrecht et al. 2010].
Other therapeutic approaches
Irradiation and surgery
Radiotherapy and surgical resection are mainly used as additional treatment modalities synchronous or in sequence with a systemic therapy [Allen et al. 2001; Swinnen, 2000; Tsai et al. 2001]. For PTLD localized to a single site, radiotherapy and surgery offer a curative approach together with immunosuppression reduction. A retrospective analysis of 30 patients treated with surgery and IR reported a 3-year overall survival of 65%. All patients submitted to surgery had stage I or II disease and received adjuvant IR after complete resection of PTLD lesions. Only 8/30 (27%) of patients relapsed at a median of 5 months (range 1-86) [Reshef et al. 2011]. Radiotherapy or surgical resection are also the treatment of choice in stage I plasmacytoma-like PTLD, a rare subtype of monomorphic B-cell PTLD associated with a favorable outcome in localized as well as in advanced disease [Trappe et al. 2011]. Furthermore, radiotherapy is used in the treatment of primary CNS PTLD [Cavaliere et al. 2010; Choquet et al. 2008].
Antiviral treatment
Acyclovir, ganciclovir, cidofovir and foscarnet are nucleoside analogs that have been shown to inhibit the replication of EBV DNA through inhibition of viral DNA polymerase. While the activity of acyclovir and ganciclovir is dependent on intracellular phosphorylation by virally encoded thymidine kinase, cidofovir and foscarnet need not be activated. Cells latently infected with EBV and cells of EBV-associated PTLD usually do not express thymidine kinase and thus attempts to treat PTLD with acyclovir and ganciclovir have proven ineffective. However, refractory EBV-associated lymphomas and PTLD have been treated with concurrent arginine butyrate and ganciclovir [Perrine et al. 2007]. Arginine butyrate selectively induces expression of thymidine kinase, making latently infected B cells and EBV-positive neoplasms vulnerable to ganciclovir treatment. In this first study in different types of EBV-associated lymphoproliferations including 15 patients, 2 of 6 patients with PTLD after SOT achieved a complete response and two had a PR. The remaining two did not respond to treatment. The most common severe adverse events were related to the central nervous system and included reversible stupor or somnolence in 4/15 patients, confusion in 6/15 patients, acoustic hallucination in 1/15 patients, lethargy/fatigue in 2/15 patients and visual changes in 1/15 patients.
Foscarnet and cidofovir are active in EBV-associated lymphoproliferations and directly inhibit DNA-polymerase without prior intracellular phosphorylization. This is also responsible for the higher rate of toxicity. We have reported on our experience with foscarnet treatment for EBV-associated PTLD in a small series of four patients [Oertel et al. 2002]. Three of these patients achieved a CR with foscarnet, two after failing to respond to IR while one was ineligible for IR. Response of PTLD to antiviral treatment correlated with the expression of lytic phase antigen BZLF1/ZEBRA protein, an early antigen of lytic EBV activity. More importantly, antiviral therapy is an attractive treatment approach in the clinically rare setting of primary EBV infection associated with PTLD [Trappe et al. 2009c]. The initiation of efficient antiviral therapy is usually accompanied by a rapid decrease in viral load in these patients. However, additional IR and application of IVIg may be useful to improve response [Trappe et al. 2009c].
Interferon alpha
IFN-alpha has proven useful in the treatment of EBV-associated PTLD in case reports and a few series using IFN-alpha alone or (more often) in combination with other treatment approaches [Swinnen et al. 2008; Schaar et al. 2001; Cantarovich et al. 1998; Davis et al. 1998; O’Brien et al. 1997; Taguchi et al. 1994]. In a phase II trial published in 2008 [Swinnen et al. 2008], 13 patients unresponsive to an upfront reduction of immunosuppression were treated with three cycles IFN-alpha 2b (3 million IU/m2 daily on days 1–28) followed by six cycles IFN-alpha maintenance treatment for patients achieving CR. Two of 13 (15%) patients achieved CR and another 2/13 (15%) achieved a PR, a response rate of 30%. One of two (50%) of patients in CR relapsed after 20 months. Three possibly IFN-alpha associated deaths (nonneutropenic sepsis, acute myocardial infarction and allograft vasculopathy, acute rejection) resulted in a TRM rate of 23%. Acute rejection episodes occurred in a total of 2/13 (15%) of patients. Other frequent grade 3/4 toxicities included an increase in creatinine in 4/13 (31%) patients, neutropenia in 4/13 (31%), fatigue in 4/13 (31%), weakness in 3/13 (23%), hypotension in 2/13 (15%), seizures in 1/13 (8%) and somnolence in 1/13 (8%) but usually were manageable with treatment interruptions and dose reductions. Thus, IFN-alpha is associated with a relatively low antitumor activity but considerable toxicity and therefore is no longer generally recommended.
Anti-IL-6 antibodies
IL-6 neutralizing monoclonal antibodies have been successfully used therapeutically in an observational study involving 12 patients with polymorphic PTLD [Haddad et al. 2001]. Treatment tolerance was good, and no major side effects were observed. CR was observed in 5/12 patients and PR in 3/12 patients. CNTO 328, an anti-IL6 monoclonal antibody, is currently also evaluated in a number of other solid and hematological malignancies.
EBV-specific T-cell approaches
Cytotoxic T lymphocytes (CTLs) that recognize both latent and lytic viral antigens are important in controlling EBV reactivation. EBV-specific CTLs are readily detectable in the peripheral blood of healthy seropositive carriers, but in transplant recipients, who require immunosuppressive drugs, the activity of virus-specific CTLs is suppressed, thus predisposing the patients to PTLD. In consequence, donor lymphocyte infusion (DLI) [Papadopoulos et al. 1994] or EBV-specific CTL transfer [Heslop et al. 1996; Rooney et al. 1995] has provided a relatively safe means to treat PTLD after allogeneic bone marrow transplantation, restoring EBV-specific T-cell control. For SOT recipients, however, EBV-specific CTLs are not as easily available. There have been several attempts to generate autologous EBV-specific CTLs to treat PTLD after SOT. A first multicenter clinical trial using EBV-specific CTLs generated from EBV-seropositive blood donors to treat patients with EBV-positive PTLD on the basis of best HLA match and specific in vitro cytotoxicity has been published [Haque et al. 2007]. A total of 33 patients were enrolled after failure of IR or conventional therapy. Twelve patients had additional rituximab and/or antiviral treatment, and eight had chemotherapy and/or radiotherapy. With the exception of three patients receiving concurrent rituximab and three patients with continued immunosuppression dose reduction, all other patients had stopped all forms of therapy 2–8 weeks before starting CTL and were considered for CTLs owing to their progressive or nonresponsive disease and, in some cases, impending graft rejection. Their immunosuppression was re-escalated before CTL infusions. Tumor biopsies from all patients were positive for Epstein–Barr Virus-encoded small RNAs (EBERs) by in situ hybridization. No adverse effects of CTL infusions were observed and the response rate (complete or partial) in 33 patients was 64% at 5 weeks and 52% at 6 months. A total of 14 patients achieved a complete remission, 3 showed a partial response, and 16 had no response at 6 months (5 died before completing treatment). These results clearly show that allogeneic CTLs are a safe and rapid therapy for PTLD after SOT, bypassing the need to grow CTLs for individual patients. The response rate is encouraging but seems to be lower than with sequential therapy using rituximab and CHOP in first-line treatment of PTLD, supporting its use in the treatment of relapsed PTLD. Further clinical trials to prove response rates and to evaluate PFS and disease-free survival are warranted.
Outlook
One focus for further improving treatment results in PTLD is the dosing of anti-CD20 monoclonal antibodies. The response to rituximab treatment is variable, depending on factors such as gender, Fcγ- and CR3-receptor polymorphisms, tumor histology and tumor burden (for an overview see Cartron et al. [2011]). Possible approaches include the application of higher doses, especially in male patients as Ng and colleagues have reported a significant increase in rituximab clearance in men treated for rheumatoid arthritis compared with women, leading to a decrease in exposure of around 30% in men [Ng et al. 2005]. Dayde and colleagues demonstrated a clear dose–response relationship, with increasing doses of rituximab leading to higher response rates and improved survival in a murine model of disseminated lymphoma-expressing human CD20 [Dayde et al. 2009]. Pfreundschuh and colleagues increased the number of rituximab infusions to achieve high rituximab levels early during treatment in a phase II trial enrolling 100 elderly patients with DLBCL [Pfreundschuh et al. 2008b]. Compared with a control group from the RICOVER trial [Pfreundschuh et al. 2008a], patients receiving the intense rituximab regimen, especially those patients with high-risk disease (IPI score 3–5), achieved a higher complete response rate and a lower rate of PD under therapy [Pfreundschuh et al. 2008b]. Another focus will be the role of cytotoxic T-cell therapy as well as that of anti-IL6 monoclonal antibodies. Finally, further clinical trials are clearly needed for relapsed/refractory disease after chemotherapy and rare PTLD subtypes such as primary CNS PTLD that currently is associated with a very poor outcome [Choquet et al. 2008].
Footnotes
Acknowledgements
The German PTLD study group (DPTLDSG) is a member of the German Competence Network Malignant Lymphomas (KML).
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
R. Trappe received research grants from AMGEN, CSL Behring, Mundipharma and Roche as well as payment for lectures and consultancy from Roche and payment for lectures from CSL Behring. H. Zimmermann has received meeting expenses from Mundipharma.