Patient-specific alterations in blood plasma cfRNA profiles enable accurate classification of cancer patients and controls

Circulating nucleic acids in blood plasma form an attractive resource to study human health and disease. Here, we applied mRNA capture sequencing of blood plasma cell-free RNA from 266 cancer patients and cancer-free controls (discovery n=208, 25 cancer types; validation n=58, 3 types). We observed cancer-type specific as well as pan-cancer alterations in cell-free transcriptomes compared to controls. Differentially abundant RNAs were heterogenous among patients and among cohorts, hampering identification of robust cancer biomarkers. Therefore, we developed a novel method that compares each individual cancer patient to a reference control population to identify so-called biomarker tail genes. These biomarker tail genes discriminate ovarian, prostate, and uterine cancer patients from controls with very high accuracy (AUC = 0.980). Our results were confirmed in additional cohorts of 65 plasma donors (2 lymphoma types) and 24 urine donors (bladder cancer). Together, our findings demonstrate heterogeneity in cell-free RNA alterations among cancer patients and propose that case-specific alterations can be exploited for classification purposes. ### Competing Interest Statement A.M., J.V. and P.M. are inventors on a patent application regarding the tail gene concept. ### Funding Statement This work was supported by Ghent University (BOF; BOF19/DOC/228), Ghent University Hospital, Fund for Scientific Research Flanders (FWO; 11C1623N to A.M., 11H7523N to P.D., G0B2820N), and Kom Op Tegen Kanker (Stand up to Cancer, the Flemish cancer society). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Ethics committee of Ghent University Hospital, Belgium gave ethical approval for this work. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are either contained in the manuscript or available online