Plasma Biomarkers in Stratifying Patients Referred Via the Lower Gastro-intestinal (LGI) Suspected Cancer Two-week Wait (2WW) Pathway

Current Challenges in CRC Diagnosis Currently, the 2WW pathway for bowel symptoms typically involves a stool-based faecal immunochemical test (FIT) before referral. While the 2WW pathway is vital for expedited diagnosis, a systematic review from 2009 revealed that only 9.5% of patients referred with lower gastrointestinal (GI) symptoms through this pathway are ultimately diagnosed with cancer. This low positive predictive value places immense pressure on an already overstretched healthcare system, leading to unnecessary invasive investigations, increased costs, and prolonged patient anxiety. There's a clear need for more accurate and less invasive diagnostic tools to better stratify patients.

Progastrin (hPG80) as a Biomarker hPG80, a circulating blood biomarker, is a precursor to gastrin and has shown promise in detecting various GI cancers, including CRC. In healthy individuals, hPG80 is typically undetectable as it's converted to gastrin. However, elevated hPG80 levels can be found in the plasma of many patients with both early and advanced GI malignancies. Studies have shown an elevated hPG80 level in CRC subjects compared to those with benign polyps. This study will investigate whether plasma hPG80 levels can accurately predict CRC or polyps in 2WW patients and distinguish the absence of cancer based on PG levels.

Transposable Elements (TEs) as Biomarkers Transposable elements (TEs), which are mobile genetic elements, are also emerging as potential cancer biomarkers. Recent research has linked TEs to various cancers, including CRC. The Dr. Madapura's lab has shown that transposable element-derived RNA signatures can be superior predictors of diseases. This study will explore the role of TEs in predicting CRC diagnosis within the 2WW referral cohort. Specifically, it will identify and evaluate TEs in the plasma of these patients as potential predictive biomarkers. The analysis will involve RNA sequencing (RNAseq) and nanopore DNA sequencing (DNAseq) of plasma samples to look for transcript signatures and epigenetic modifications of DNA.

Study Design and Population This is a prospective, observational, cohort study conducted at Barts Health NHS Trust, initially focusing on the Royal London Hospital site. The study will recruit 582 adult patients referred via the 2WW or Straight to Test (STT) pathways for suspected lower GI cancer. Eligible patients will be aged over 18 years, have no history of inflammatory bowel disease, and have a performance status of ECOG 0-2 (or 3, pending clinical assessment). Patients with a family history of CRC are not excluded. Those with a documented familial type of CRC, untreated solid organ cancers, or who are not fit for standard investigations will be excluded.

Data Collection and Analysis Upon informed consent, a 20ml venous blood sample will be collected from participants at their first clinical appointment, usually during a routine hospital visit for their 2WW diagnostic test (e.g., colonoscopy, CT colonography). This sample will be used for both PG and TE analysis. Plasma PG levels will be measured, and a subset of 100 samples (25 confirmed CRC and 75 non-cancer samples) will undergo RNAseq and DNAseq for TE analysis.