Study explores if wastewater can track colorectal cancer at population level

Researchers demonstrate that colorectal cancer–associated RNA biomarkers, including CDH1, can be detected in community wastewater using a proof-of-concept approach.

Study: Using wastewater for population-level colorectal cancer surveillance: a future research agenda. Image Credit: Siyanight / Shutterstock

A proof-of-concept feasibility study published in the Journal of Epidemiology & Community Health reveals a feasibility-based approach to detecting colorectal cancer (CRC)-related signals at the community level through wastewater surveillance systems.

For the first time, researchers have detected specific human ribonucleic acid (RNA) biomarkers associated with colorectal neoplasia in community wastewater, drawing on biomarkers used in the highly sensitive multitarget stool RNA (mt-sRNA) assay used for early CRC detection in adults aged 45 and older.

The detection of biomarkers such as cadherin 1 (CDH1) highlights the feasibility and potential utility of this method to complement traditional screening, offering a future research avenue for community-driven public health interventions and targeted prevention programs, particularly as CRC rates rise among younger populations.

Limitations of Traditional CRC Screening Methods

CRC remains a major health threat, and early detection is crucial for improving outcomes. Traditional screening, via colonoscopy or stool tests, depends on individual participation and is often limited in low-resource settings.

Wastewater surveillance provides a potential population-level adjunct approach, detecting RNA biomarkers shed into sewage to explore patterns related to community-level CRC burden rather than directly measuring individual risk. By potentially reducing reliance on individual compliance, this approach may enable broader, equitable, community-focused CRC screening and population-level risk monitoring. 

Previous research has focused on cancer drugs or non-specific mitochondrial deoxyribonucleic acid (DNA) in wastewater. Targeting CRC-specific biomarkers could, in future studies, strengthen early detection and complement existing prevention strategies.

Study Design and Wastewater Sampling Methods

In this retrospective study, researchers evaluated the feasibility of detecting human RNA biomarkers for CRC in neighbourhood-level wastewater, aiming to track signals potentially associated with community CRC burden.

Using traditional methods, the investigators selected RNA biomarkers informed by the multitarget stool RNA assay for exploratory population-level CRC surveillance. They collected wastewater samples from four residential sewer sheds, three high-incidence CRC clusters, and one control region.

RNA extracted from the samples underwent digital polymerase chain reaction (PCR) to quantify biomarker expression. These biomarkers include glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a housekeeping gene, and CDH1, associated with colorectal neoplasia.

The team collected CRC data from a specialized care centre between 2021 and 2023. They then mapped patients’ residential addresses to identify areas with a higher incidence of CRC. The first two clusters represented neighborhoods with more than four cases within half a mile of the centre.

The investigators selected the third cluster using statewide cancer registry data and matched demographics, representing a high-incidence area that did not fully overlap with the care centre clusters. 

The fourth cluster (control) encompassed a sewer shed without identified cases in the specific datasets used, although residents may still have had CRC diagnosed or treated outside these sources.

To complement this, researchers analyzed state-level cancer registry data from 1995 to 2018 to calculate sex- and age-standardized CRC rates across Kentucky census tracts. Using the Getis-Ord Gi* spatial statistic, they identified additional high-incidence areas, confirming the three CRC clusters and supporting the selection of a control sewer shed.

All the sewersheds were located in residential areas. The investigators obtained population demographic data using the Business Analyst platform by the Environmental Systems Research Institute (ESRI). They collected wastewater samples at three time points across the day (morning, mid-morning, and early afternoon) from a manhole in each sewer shed to improve coverage.

The sewers included both integrated stormwater–wastewater systems and separate sanitary lines. These samples captured RNA biomarker patterns over time and across communities, although sampling was limited to a single day, with a small number of samples and no statistical testing, supporting wastewater surveillance for CRC monitoring.

Detection of CRC Biomarkers in Wastewater

The wastewater analysis confirmed the presence of human RNA biomarkers at detectable levels in all samples. GAPDH averaged approximately 52 copies per microliter, confirming consistent RNA extraction.

Colorectal neoplasia-related CDH1, normalized to GAPDH, was generally low in the morning and mid-morning samples. In contrast, CDH1 levels spiked in the early afternoon samples obtained from the first cluster.

Average normalized CDH1/GAPDH values differed across clusters. The team detected levels of 20.0 in the first cluster, 2.2 in the second, and 4.0 in the third cluster, compared to 2.6 in the control cluster.

The first cluster, which included known patients from the specialized care centre, displayed the highest CDH1 signal, aligning with clinical data. In the control sewershed, CDH1 remained detectable but generally lower, with 2 of 3 measurements below 1.0, indicating low background levels. The pronounced CDH1 signal in the first cluster suggests, but does not establish, that wastewater monitoring may reflect underlying local disease burden.

Implications for Public Health and CRC Monitoring

The findings show that CRC-associated RNA biomarkers, including CDH1, can be detected in community wastewater, supporting a feasible but preliminary and hypothesis-generating, neighborhood-level approach to epidemiological surveillance.

Early evidence suggests that non-invasive monitoring can potentially contribute to, rather than replace, traditional CRC detection and support population-level risk assessment. 

By identifying high-risk areas with minimal patient participation, this method could, if validated, eventually inform public health policy, optimize resource allocation, and guide targeted screening programs.

Future Research and Validation Needs

Future research should expand the number of sampling sites and frequency, validate the sensitivity and specificity of wastewater biomarkers, integrate findings with cancer registry data to refine spatial mapping of CRC risk, and carefully address ethical and privacy considerations.

Larger, longitudinal studies with repeated sampling and stronger linkage to confirmed CRC incidence will be essential to determine validity, sensitivity, specificity, and real-world applicability. These steps will help establish a robust, evidence-based framework for community-level CRC monitoring and support the development of targeted public health interventions.