Post-transplantation Lymphoproliferative Disorder (PTLD): In the Liver Transplant Recipient

Abstract

Post- transplantation lymphoproliferative disorders (PTLD) are uncommon neoplasms that complicate the post transplantation period. The incidence of PTLD and outcome post liver transplantation is sparsely described. Children who undergo liver transplantation are at higher risk of PTLD than adults. Risk factors for PTLD include the level of immunosuppression and Epstein–Barr virus status. Immunosuppression in post-transplant patients can cause uncontrolled expansion of B cells. The diagnosis requires high degree of clinical suspicion, radiological evaluation, and tissue biopsy. Risk reduction depends mainly on decreasing patients' exposure to aggressive immunosuppressive regimens and is the initial step in management. Rituximab with or without chemotherapy is the mainstay of treatment. In refractory or persistent disease, alternative treatment options like adoptive immunotherapy and autologous stem cell transplant have been explored. Prognosis is determined by clonality of the PTLD and severity of the disease.

Post -transplantation lymphoproliferative disorders (PTLD) are lymphomas that develop in the post-transplant setting as a result of the immunosuppressed state. In post liver transplant (LT) patients, these neoplasms are rare and associated with increased mortality. Early clinical suspicion, monitoring and diagnosis are required for better outcomes. Here, we look at the incidence, pathophysiology, evaluation and management of PTLD in liver transplant recipients (LT-PTLD).

PREVALENCE OF LT-PTLD

PTLD develops due to excessive B cell growth caused by immunosuppression in the post transplantation period.¹ It can manifest in various forms ranging from lymphoid hyperplasias to invasive lymphomas which may be fatal.²

PTLD is noted in 1%–10% of post solid organ transplantation (SOT) patients and 1%–5.5% in those who have undergone LT.^3,4 The incidence is significantly affected by the transplanted organ, with intestinal transplants (20%) having the highest incidence, followed by lung (3.0%–10.0%), heart (2.0%–8.0%), liver (1.0%–5.5%), pancreas (0.5%–5.0%) and kidney transplants (0.8%–2.5%).^2,4,5 It is the most prevalent de novo malignancy post-transplant in children and second most common in adults.²

In the pediatric population, PTLD is seen in 4.6%–20%, with a death rate of 6.7%–60%.⁶ A study done in Iran included 53 patients with PTLD which included 40 in the pediatric age group. The incidence of PTLD in this study was 6.25% (pediatric) versus 1.18% (adult).⁷ The largest case series from Japan Tajima et al. evaluated 1849 patients who received LT, of which 67 developed PTLD (45 pediatric [5.1%] and 22 adults [2.3%]).³ (see Table 1)

Table 1.

Summary of Studies on Post Transplantation Lymphoproliferative Disorder in Liver Transplant Recipients.

Study	Number of patients with LT-PTLD	Interval between LT and PTLD	Prognostic factors in LT-PTLD	EBV positive PTLD	Biopsy characteristics	Treatment	Outcomes
Tajima et al.3 2020	Total: 67/1849 Pediatrics: 45 [5.1%] Adults: 22 [2.3%]	19 days to 24.5 years (median, 23 months)	Age at diagnosis >18 PS ≥ 2 Monomorphic PTLD				Died: 30/67
Kremers et al.48 2006	37/1206	3 months to 15.5 years	LT for acute fulminant hepatitis during the first 18 months following LT Immunosuppression with high-dose steroids and OKT3	22/37	Early lesion −1/34 Monomorphic – 29/34 Polymorphic −4/34	RIS-24/37 Rituximab −5 Chemotherapy −11/37 Surgery-13/37 Radiation – 4	Died: 20/37
Mumtaz et al.27 2015	32/1372	3–240 months (median, 60 months)	EBV positive patients – poorer survival	17/32	Diffuse large B cell lymphoma −21 [65%], Burkitt type, diffuse large T cell type, and T and B cell mixed monoclonal lymphoma (n = 2 each [6%]) Monoclonal B cell type lymphoma- 1 Hodgkin disease- 4 [13%])	RIS -15 Stopping IS – 9 Change in IS to Sirolimus – 7 Chemotherapy – 23, Surgery – 4	Died: 11/32
Hsu et al.6 2019	16/110 (All pediatrics)	3.3 months to 10.6 years (median, 8 months)		15/16	Early lesion −1 (6.3%) Polymorphic −6 (37.5%) Monomorphic – 8 (50%) Hodgkin's lymphoma −1 (6.3%)	RIS- 16 Rituximab – 6 Chemotherapy-9	Died-3/16
Dorado et al.49 2017	10/851 (All adults)	12 months to 12 years (median, 2.9 years)		5/10	Early lesion – 1 Polymorphic – 2 Monomorphic – 7	RIS- 1 Change to sirolimus – 3 Rituximab – 3 Chemotherapy – 2	Died – 5/10
Marino et al.50 2010	10/766(All adults)	1 year to 8 years (median, 5years)		1/6 sampled tissues	Polymorphic −2 Monomorphic – 7 Hodgkin's lymphoma – 1	RIS -10 Rituximab −5 Chemotherapy – 7 Surgery −3	Died-4/10

LT – Liver transplant, PTLD – Post transplant lymphoproliferative disorder, EBV – Epstein–Barr virus, IS - Immunosuppression, RIS – reduction of immunosuppression, PS – Performance score.

The data on LT-PTLD from India is sparse and is restricted to a few case reports.8, 9, 10, 11 Two cases of LT-PTLD have been reported from North India^9,12), three cases from South India^8,11,13 and one from Maharashtra.¹⁰

DIFFERENCE BETWEEN PEDIATRIC-ONSET VERSUS ADULT-ONSET LT-PTLD

Pediatric-onset LT-PTLD is more common (5.1% versus 2.3%)³ and tends to occur within a year following transplant. In general, PTLD occurs earlier in the post LT period in children compared to adults. Another study on 1207 children who underwent LT showed that 49 (4%) developed PTLD, and the mean age of those with PTLD when they underwent LT was 4.93 ± 1.07 years which was lower than those who did not develop PTLD (7.80 ± 5.54).¹⁴ When compared to adults, LT-PTLD in children was associated with a better prognosis, as majority of them developed non-monomorphic PTLDs (discussed below). This variant is associated with higher survival rates and more favourable outcomes.³

RISK FACTORS

Key risk factors in the post LT setting were the level of immunosuppression and Epstein–Barr virus (EBV) serology of the recipient. First year post LT is another important risk factor.^3,15,16

When a seropositive donor liver is transplanted into a seronegative individual (D+/R-), there is a high risk of the transplanted liver containing EBV infected B cells which proliferate.¹⁵ This is exacerbated in patients on immunosuppressive regimens that target the T cells like CD3 monoclonal antibody (OKT3) and anti-thymocyte globulin which causes loss of T cell function. There is also a decline in EBV-specific cytotoxic T lymphocyte (CTL), which causes viral reactivation and PTLD.¹⁷

PATHOGENESIS AND PATHOLOGY OF LT-PTLD

EBV plays an important role in development of PTLD. Majority (85%) are of B cell origin and approximately 80% of these are associated with EBV.¹⁸

EBV-positive PTLD

EBV (γ-herpes virus) promotes B cell growth and transformation. In healthy people, oropharynx is the site of initial lytic EBV infection, involving active replication, virion generation and cell lysis. This evokes a strong immune response clearing the infection. Persistence of EBV in infected B lymphocytes results in latent infection. In latency 0, the EBV DNA persists in the nucleus and integrates with the host genome which is responsible for its protracted survival.

Three more latency phases, in addition to latency 0, are defined as per the expression of protein patterns in the EBV virus.¹⁹ Latency III, often known as ‘the growth programme’, occurs in the lymph nodes with expression of all nine viral proteins. This causes B cells to proliferate and form blasts. In this programme, EBNA-2 (EBV nuclear antigen) activates latent gene transcription by increasing LMP (latent membrane protein) −1 and 2 and other cellular proteins which finally lead to B cell proliferation and alteration. LMP-1 has been shown to serve as an oncogene in transgenic mouse models. LMP-2 suppresses EBV reactivation in dormant cells.²⁰ This latency III programme is responsible for EBV-positive PTLD. Latency II is a ‘default programme’ with LMP-1 expression but no EBNA2 or EBNA3, which helps in avoiding detection of the virus by cytotoxic T cells. Latency I has minimal EBV protein expression; which allows them to survive asymptomatically in the host.²⁰

Normally, reactivation is contained rapidly by EBV-specific CTLs’. However, in post LT immunosuppressed patients, there is loss in frequency and function of these cells leading to uncontrolled proliferation and PTLD.²¹

EBV-negative PTLD

There is paucity in knowledge regarding its pathogenesis. However, it is considered to be caused by unidentified viruses or EBV loss, wherein the initial lympho-proliferation induced by EBV leads to newer mutations and changes over time, perhaps leading to EBV-independent cell replication.²²

Pathology of LT-PTLD

PTLDs can be nondestructive (plasmacytic hyperplasia, infectious mononucleosis, and florid follicular hyperplasia), polymorphic, monomorphic, or classical Hodgkin's lymphoma, according to the WHO 2017 classifi-cation.²³

Plasmacytic hyperplasia: The histology shows maintained architecture with a predominance of polyclonal B cells. There is no evidence of cytogenetic abnormalities.

Infectious mononucleosis: There is no architectural effacement with mainly polyclonal B cells on histology. A simple cytogenetic abnormality may occur in rare cases.

Florid follicular hyperplasia: The architecture is maintained with polyclonal B cells and occasional monoclonal B cells. They frequently test positive for EBV. Cytogenetic abnormalities may be seen occasionally.

Polymorphic PTLD: There is architectural distortion with varied clonality including polyclonal or monoclonal cells. It does not meet the criteria for Non-Hodgkin's lymphoma (NHL). Cytogenetic abnormalities like BCL6 somatic hypermutations may be observed.

Monomorphic PTLD: There is architectural distortion with tumor containing only monoclonal cells (B or T cells). They meet the criteria for NHL.

Classic hodgkin lymphoma (cHL) like PTLD: There is architectural distortion with tumor containing only monoclonal cells and histology similar to cHL. They are least frequently seen. (Figure 1)

Figure 1.

Typical histopathological images of an EBV- positive PTLD – Hodgkin's Lymphoma after solid organ transplantation; a. Scattered large cells in a polymorphic infiltrate including few binucleated reticulo endothelial (RS) cells (arrow) and mononuclear RS cells (arrowhead) (hematoxylin-eosin, magnification 20×); b. Large cells show membrane and Golgi positivity for CD15; c. Large cells show membrane and Golgi positivity for CD30; d. Large cells show membrane and Golgi positivity for Epstein–Barr virus latent membrane protein 1 (EBV LMP1). (Image courtesy: Dr. Elanthenral Sigamani, Department of General Pathology, Christian Medical College, Vellore).

ASSOCIATION BETWEEN CALCINEURIN INHIBITORS (CNIS) AND LT-PTLD

Few studies have suggested that tacrolimus use was probably more commonly associated with PTLD. A study done by Jeffery et al. included 324 pediatric post-heart transplantation patients, out of which 109 (34%) were treated with tacrolimus. 16/109 (15%) treated with tacrolimus developed PTLD while among those treated only with cyclosporine (213/324), 17/213 (8%) developed PTLD. A significant association was noted between tacrolimus and PTLD, hazard ratio of 4.04 (P = 0.0001).²⁴ Another study on pediatric post-LT patients found that tacrolimus levels >11.1 ng/mL predicted survival in PTLD patients.⁷ However, a cochrane review of 16 randomised trials concluded that the incidence of LT-PTLD was not different between those receiving tacrolimus or cyclosporine.²⁵ Thus, data on the superiority of one immunosuppressive drug over the other in decreasing the risk of LT-PTLD is lacking and conclusions cannot be made.

DIAGNOSIS OF PTLD

Early detection is critical for improved outcomes, requiring vigilance in the post LT period.

Clinical Features

PTLD presentation can be varied based on the type and areas of involvement. It is often characterised by non-specific symptoms like fever (50%), lethargy and weight loss. Lymphadenopathy is seen in 30%. Depending on the organ involved, the presentation could be organ dysfunction and/or compressive symptoms of surrounding structures. Few patients may present with intestinal perforation (15%) which can be life threatening.²

A study on 170 LT-PTLD patients showed that a single site was more commonly involved than multiple sites (58% versus 41% respectively) with lymph nodes (35%) being the most common site. The gastrointestinal tract was affected in 25% with liver and spleen involvement being noted in 16%. Only 4% presented with central nervous system (CNS) involvement.²⁶ In another study, out of 42 patients who developed LT-PTLD only 6% had liver involvement.²⁷

Physical examination and imaging showing a mass in post-transplant patients is likely to be PTLD. Generalised lymphadenopathy may also point toward a PTLD.²⁸ Various radiological modalities have been used in the diagnosis of PTLD.²⁹ A positive PET scan can be helpful in the diagnosis. A rising EBV DNA titre in the appropriate clinical scenario could point to a diagnosis of PTLD. A tissue sample, ideally an excisional biopsy, confirms the diagnosis. Tissue should be sent in for EBV testing, cytogenetics, and antigen receptor gene rearrangement studies. After PTLD is diagnosed, a pre-treatment workup is done.^3,14

PREVENTION/RISK REDUCTION OF PTLD

Prevention largely depends on decreasing patients' exposure to aggressive immunosuppressive regimens.

Reduction in Immunosuppression

The American Society of Transplantation (AST) advises reduction of immunosuppression as the preferred preemptive intervention, though data is insufficient to prescribe specific protocols for immunosuppression reduction.³⁰

In a patient with a rising EBV load on a high level of immunosuppression, a reduction of immunosuppression may be considered. Baker et al. showed that rates of PTLD decreased from 16% to 2% when immunosuppression was decreased in patients with a high EBV load. Only one out of the 73 post LT patients in this study developed graft rejection.³¹ Therefore, before reducing immunosuppression, the possibility of graft failure must be considered.

Antiviral Prophylaxis

The role of antiviral prophylaxis is poorly understood and lacking in data. A review of 31 studies on SOT recipients, which compared antiviral prophylaxis against EBV versus no prophylaxis showed no significant difference in incidence of EBV-positive PTLD (RR-0.95, 95% CI 0.58–1.54). The duration of antiviral prophylaxis also did not have an effect on the rates of PTLD development. The groups that received prophylaxis for more than 100 days (RR 0.47, 0.18–1.23) as compared to those who received for less than 100 days (RR 0.50, 0.11–2.34) revealed no difference in incidence of PTLD. Thus, this meta-analysis concluded that there was not enough evidence to justify the routine use of antivirals to minimise PTLD in SOT recipients.³²

The AST 2019 guidelines do not recommend antiviral prophylaxis in EBV mismatched individuals to prevent PTLD.³⁰

ROLE OF EBV MONITORING IN POST LT PATIENTS

There are no guidelines presently recommending routine EBV monitoring in post-LT patients as well as no consensus on the criteria for high-risk patients or the cut-off for EBV positivity.

Studies on effectiveness of quantitative EBV viral load in detecting early PTLD are limited. EBV-positive PTLD individuals have an increased EBV viral load as demonstrated by Wagner et al. who demonstrated the median EBV viral load in individuals with PTLD (n = 5) to be 3225 copies/100 microL plasma. In the immunocompromised controls with no PTLD, median EBV viral load was 30copies/100mcL plasma in those with primary EBV infection (n = 9) and 20 copies/100 mcl plasma in reactivated EBV infection (n = 20).³³ This indicates that an early diagnosis of PTLD could be made by quantifying the EBV viral load through polymerase chain reaction in individuals with risk factors for developing this condition. Another study in which five out of 39 post LT children (median age at LT - 1.3 years) developed PTLD showed that a peak EBV viral load of > 4100 copies/mcg peripheral blood mononuclear cells DNA, less than 3 months post- LT was associated with PTLD.³⁴ EBV viral load has a good sensitivity for establishing a diagnosis of EBV-positive PTLD in high-risk SOT recipients but has poor specificity, and negative predictive value of > 90%.^35,36 In a study by Schaffer et al. on 197 post-LT patients, EBV DNAemia was noted in 72% patients who were asymptomatic within 100 days post-LT, however no one developed PTLD during the study period. This study concluded that though EBV DNA levels could be elevated in post-LT patients, it did not indicate PTLD and thus routine monitoring in these patients was unnecessary as it did not aid in predicting mortality or morbidity.³⁷

As per British Transplantation Society (BTS) guidelines, ‘in adults there is little evidence to support the routine use of surveillance EBV PCR outside the allogeneic haemopoietic stem cell transplantation setting’.³⁵ The EASL guideline on LT mentions that pre-emptive monitoring should be considered when there are risk factors like EBV serology mismatch.³⁸ However, till date there are no specific Indian recommendations on EBV monitoring in Post LT patients.

MANAGEMENT OF PTLD AND THEIR OUTCOMES

Decreasing patients' exposure to aggressive immunosuppressive regimens is the initial step in management. This is followed by rituximab monotherapy or chemo-immunotherapy or chemotherapy based on various factors like histology, stage and location, status of the graft, and post-LT duration. Surgery/radiotherapy could be considered in localised diseases if feasible. (Figure 2)

Figure 2.

Algorithm of diagnosis and management of PTLD.

Reduction of Immunosuppression

An initial step is to immediately reduce immunosuppression (RIS) if it is safe to do so in order to partially restore T cell activity. It may show good response in those with early-onset PTLD and low disease burden typically the non-destructive type of PTLDs. There are no universal guidelines or protocols on tapering of immunosuppression and is mostly individualised to each patient based on type of SOT and disease severity.²³ Studies mention decreasing immunosuppression to the lowest possible dose (around 25%–50% of the starting dose) keeping in mind graft rejection concerns.¹⁵ RIS has shown an overall response rate of 45% with 37% showing full response and relapse rates of 17% in patients who achieved complete remission.³⁰

When RIS is the only first treatment, response is assessed within 2-4 weeks by examining changes in tumor size, lactate dehydrogenase (LDH), and EBV load.³⁹

If there is no response, alternative strategies are implemented. If patients with low risk factors achieve complete remission (CR), no additional therapy may be required. These patients are closely monitored for graft rejection.⁴⁰

Rituximab

Rituximab (monoclonal antibody against CD20) monotherapy has a role in the treatment of CD20-positive PTLDs with remission rates ranging from 44% to 65%. The British Society for Hematology recommends rituximab monotherapy in individuals diagnosed with CD20-positive PTLD with poor response to initial therapy with RIS. In patients who achieve CR or complete metabolic remission (CMR) after four cycles of weekly standard-dose rituximab, four further three-weekly cycles is recommended.⁴⁰ However, some patients on or after rituximab therapy may require chemo-immunotherapy.

Chemotherapy

For CD20-positive PTLD, chemotherapy is combined with rituximab. R–CHOP (rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone) is the recommended regimen, although CHOP (without rituximab) is administered to CD20 negative PTLD patients. Randomized trials evaluating efficacy of different chemotherapy regimens are lacking. The response rates with CHOP treatment, with or without rituximab, ranges from 65 to 100% with very less incidence of graft rejection.⁴¹

Local Control

Surgery/Radiation therapy may be effective in some cases of PTLD that are localised or involve the CNS. Primary CNS lymphoma post-transplant has a mortality of up to 88% and is very difficult to treat.⁴² In children with CNS PTLD, high-dose methotrexate has shown some benefits.⁴³

Adoptive Immunotherapy

An alternative therapeutic option for EBV-positive PTLD is EBV-specific CTL immunotherapy which has low graft rejection rates. In this immunotherapy, autologous EBV-directed CTLs are generated either from the recipient's cells or a bank of partially HLA-matched EBV-specific CTLs which destroy the aberrant B cells. This also leads to a reduction in EBV DNA load.⁴⁴

A study on 33 patients who underwent autologous immunotherapy after failing initial therapy had 52% overall response rate (ORR).⁴⁵ Refractory PTLDs’ from the same study treated with third-party allogeneic EBV-specific CTLs showed an ORR of 75% with overall three-year survival of 60%.⁴⁶

Role of Autologous Stem Cell Transplantation (auto-SCT) in PTLD

Refractory PTLDs includes a group of patients who are difficult to treat with no clear management guidelines. There is no data to guide decision-making. It is also unclear how salvage chemotherapy and autologous SCT affect the function of the transplanted solid organ.

Twenty one patients with PTLD post-SOT, who underwent auto-SCT were retrospectively studied. The SOTs were kidney 10/12 (48%) and liver 5/21 (24%). At least two lines of treatment (range: 1–4) were given prior to auto-SCT. Twelve deaths were reported with non-relapse mortality (NRM) at 100 days and 1 year of 14% and 24%, respectively. According to this study, while auto-SCT is viable and may have therapeutic benefits, it is associated with significant NRM, mainly infectious. Hence, stringent patient selection criteria and a multi-disciplinary approach are required.⁴⁷

Prognosis

The majority of data on the outcome of PTLD is based on retrospective studies. Prognosis is determined by clonality (monomorphic versus polymorphic) and the severity of the disease. According to Tajima et al.'s study of 67 post-LT patients (45 pediatric and 22 adults), the overall survival rate of post-LT-PTLD at three, five and ten-years in the pediatric and adult groups was 81%, 79%, and 71%; and 61%, 38%, and 28%; respectively.³

Monomorphic PTLD has a greater mortality of roughly 80%, while T cell lymphomas have an exceedingly dismal prognosis. The prognostic factors in LT-PTLD are age at diagnosis ≥ 18 years, poor clinical status (performance score > 2) at diagnosis, and type of PTLD (monomorphic type).³

PTLDs are uncommon in post LT patients. Early recognition in high risk patients could enable early diagnosis and treatment which may impact the overall survival.

AUTHOR CONTRIBUTION STATEMENT

Asisha Janeela. M, Concept and design, Literature Review, Preparation of manuscript, Critical writing/intellectual content, Review and Final approval.

Fouzia N.A, Literature Review, Critical writing/intellectual content, Review and Final approval.

Uday George Zachariah, Concept and design, Literature Review, Preparation of manuscript, Critical writing/intellectual content, Review and Final approval.

Conflicts of interest

None of the authors have any conflict of interest to disclose.

Acknowledgements

Dr. Elanthendral Sigamani, Department of General Pathology, Christian Medical College, Vellore, India.

Funding

There was no financial grant received for conducting this review.