Detection of bowel cancer marker in wastewater may offer new early warning system

Detection of a bowel cancer marker (CDH1) in wastewater may offer a new community-level early warning system for the disease, suggests a proof-of-concept study published in the Journal of Epidemiology and Community Health. Wastewater surveillance could complement traditional screening methods and could help target areas for cost-effective, practical community screening, particularly amid rising rates of the disease among young people, say the researchers.

In the U.S. alone, there are an estimated 154,000+ new cases of bowel cancer every year, making this the third most common cancer and the second leading cause of cancer-related deaths in the country, as the disease is often diagnosed at a late stage, highlight the researchers.

Wastewater in sewers can be used to monitor a wide range of biological compounds shed in urine and feces, but it’s not known if such an approach might work for community surveillance of bowel cancer, explain the researchers.

How the study was set up

To find out, they reviewed the details of patients treated with bowel cancer at a tertiary care center in Jefferson County, Kentucky, between 2021 and 2023, to identify geographical clusters of high incidence rates of the disease.

Clusters were defined as areas with more than four bowel cancer cases within a half-mile radius. Next, sex- and age-standardized rates of bowel cancer were calculated from state cancer registry data for diagnoses captured between 1995 and 2018. Three geographical areas of high bowel cancer incidence and one area where none of the tertiary care or state cancer registry patients lived were selected for neighborhood wastewater analysis.

Sampling wastewater for cancer markers

Wastewater samples (175 ml) were collected three times from each of four sewersheds at 7:00, 10:00, and 13:00 hours over the course of one day (26 July 2023). The researchers analyzed the samples for human RNA biomarkers: CDH1, which is associated with cancer; and a general cell maintenance marker GAPDH (glyceraldehyde 3-phosphate dehydrogenase) to use as a control.

All the samples from all four clusters showed detectable levels of these compounds. Average levels of CDH1/GAPDH markers for the three clusters were 20 (cluster 1), 2.2 (cluster 2), and 4 (cluster 3), compared with 2.6 in the comparison cluster.

Cluster 1 had more than double the number of known tertiary care center patients per 100 people when compared with the other two clusters, which might explain the wide variation in the figures, say the researchers. Some residents in the control cluster may also have been treated for cancer elsewhere.

Limitations and future potential

This is a proof-of-concept study, and further research will be needed, the team cautions, acknowledging various limitations to the findings. It’s not clear how the CDH1:GAPDH ratio in wastewater specifically relates to new cases of bowel cancer, and whether this represents diagnosed or undiagnosed cases, for example.

The small sample size and geographical scope limit the wider applicability of the findings, while the sensitivity and specificity of wastewater-based epidemiology for detecting bowel cancer biomarkers require validation in larger groups of people, the researchers point out.

But they emphasize, “The recent trend of increasing [colorectal cancer] incidence in younger populations underscores the need for improved public health approaches. While existing screening methods like colonoscopy and stool-based tests remain effective, their reliance on individual compliance presents challenges, particularly in communities facing structural and social determinants of health barriers.”

They suggest, “Detecting elevated [colorectal cancer] markers across broader community zones, before high incidence is recorded by tertiary care centers or state cancer registries, could help target areas for practical, cost-effective, community screening. This approach may enable early diagnosis while also identifying regions with a lower likelihood of case discovery, enabling timely clinician alerts.”