De Novo Cancer in Liver Transplant Recipients (DETECT) - A ScandiaTransplant Collaboration



Background
Liver transplantation is a complex surgical procedure and the only curative treatment for many patients with chronic end-stage liver disease and acute liver failure. Short-term survival for liver transplant recipients has improved markedly over the past decades. In contrast, there has been no improvement in long-term survival over the same period. De novo cancer is one of the leading causes of death after liver transplantation and the risk of cancer in liver transplant recipients is twice the cancer risk in the general population. The immunosuppressive medication, used to prevent organ rejection, is considered a key factor increasing the risk of de novo cancer. Due to high incidence of de novo cancer, screening may be relevant in liver transplant recipients. Currently, the method of choice is Positron Emission Tomography-Computed Tomography (PET-CT), however, the modality is costly and carries a risk of false positive results. We propose genome-wide cell-free DNA fragmentation as a screening method for de novo cancer in liver transplant recipients. The method can be used in blood samples and differentiates cell-free DNA from healthy individuals and patients with cancer. Circulating tumor DNA fragments are continuously shed into the bloodstream and have a short lifespan of only a few hours, making it an optimal real-time marker, reflecting the tumor burden. Applying sequencing technology to cell-free DNA extracted from blood, the whole genome is explored. To determine if the blood contains ctDNA, we utilize that the genome of a tumor typically differs from that of the normal genome counterpart at thousands to millions of positions. In our recent study, published in Nature, the approach was used for early and accurate detection of seven different cancer types. The method has never been investigated in liver transplant recipients and has potential to enable screening for cancer by a simple blood sample. Blood samples can be collected locally, with minimal discomfort and risk for the patient. In addition, the method carries health economic advantages since a blood sample is performed at low costs and only patients with positive analysis would be further investigated with PET-CT, minimizing the risk of false positive results.


Aims
The overall aim of the study is to assess genome-wide cell-free DNA fragmentation as a screening method for de novo cancer and potentially reduce cancer related mortality in liver transplant recipients. To obtain this we will I. Determine cell-free DNA fragmentation profiles in liver transplant recipients with cancer and liver transplant recipients without cancer II. Investigate if cell-free DNA fragmentation can be used to identify liver transplant recipients with de novo cancer III. Investigate serial blood samples to explore if cell-free DNA fragmentation can be used to identify cancer at an asymptomatic stage.

Methods
The study is a prospective, national and multicenter case-control study in liver transplant recipients from five Scandinavian liver transplantation centers (Copenhagen, Oslo, Gothenburg, Stockholm, and Helsinki). In Denmark, Rigshospitalet has national coverage, being the only center performing liver transplantation. Blood samples to perform cell-free DNA fragmentation analyses are stored in a dedicated biobank, collected pre-liver transplantation and sequentially post-liver transplantation during annual follow up (n=932). Data on demographics, de novo cancer and risk factors are retrieved from electronic health records, cancer registries and the ScandiaTransplant database. Due to the rarity of the event, we will perform a nested case-control study, cases are identified as liver transplant recipients with de novo cancer and controls are recipients without de novo cancer. Cases will be frequency matched with controls 1:3, based on time from liver transplantation to biobank sample, age and sex. Based on a median follow-up of six years in the biobank at the time of analyses, we expect to identify 67 cases (six-year incidence of 5.4%) and 201 controls (n=268). The latest biobank plasma sample before the cancer diagnosis will be evaluated using genome-wide cell-free DNA fragmentation and DELFI (DNA evaluation of fragments for early interception). In recipients where a cancer signal is measured, blood samples prior to the cancer diagnosis will be analysed to investigate if the method is able to detect cancer prior to clinical symptoms.

Implications
Compared to PET-CT, the method genome-wide cell-free DNA fragmentation would provide an easily accessible and less costly screening tool, possibly allowing early diagnosis of de novo cancer enabling curative intended intervention. The study is part of a PhD-project investigating new methods to identify liver transplant recipients with increased risk of developing de novo cancer. 

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Hans-Christian Pommergaard

Associate Professor
Kirugisk Afdeling C, Rigshospitalet