Colorectal Cancer: New Primary Care Method Predicts Onset Within Next 2 Years

TOPLINE:

A novel method combining genetic variants, symptoms, and patient characteristics is moderately successful at predicting which primary care patients are at high risk of developing colorectal cancer (CRC) within the next 2 years — without the benefit of a faecal immunochemical test (FIT). Up to 16% of primary care patients are non-compliant with FIT, which is the gold standard for predicting CRC.

METHODOLOGY:

• This study was retrospective cohort of 50,387 UK Biobank participants reporting a CRC symptom in primary care at age ≥ 40 years.
• The novel method, called an integrated risk model, used a combination of a polygenic risk score from genetic testing, symptoms, and patient characteristics to identify patients likely to develop CRC in the next 2 years.
• The primary outcome was the risk model’s performance in classifying a CRC case according to a statistical metric, the receiver operating characteristic area under the curve. Values range from 0 to 1, where 1 indicates perfect discriminative power and 0.5 indicates no discriminative power.

TAKEAWAY:

• The cohort of 50,387 participants was found to have 438 cases of CRC and 49,949 controls without CRC within 2 years of symptom reporting. CRC cases were diagnosed by hospital records, cancer registries, or death records.
• Increased risk of a CRC diagnosis was identified by a combination of six variables: older age at index date of symptom, higher polygenic risk score, which included 201 variants, male sex, previous smoking, rectal bleeding, and change in bowel habit.
• The polygenic risk score alone had good ability to distinguish cases from controls because 1.45% of participants in the highest quintile and 0.42% in the lowest quintile were later diagnosed with CRC.
• The variables were used to calculate an integrated risk model, which estimated the cross-sectional risk (in 80% of the final cohort) of a subsequent CRC diagnosis within 2 years. The highest scoring integrated risk model in this study was found to have a receiver operating characteristic area under the curve value of 0.76 with a 95% CI of 0.71-0.81. (A value of this magnitude indicates moderate discriminative ability to distinguish cases from controls because it falls between 0.7 and 0.8. A higher value [above 0.8] is considered strong and a lower value [< 0.7] is considered weak.)

IN PRACTICE:

The authors concluded, “The [integrated risk model] developed in this study predicts, with good accuracy, which patients presenting with CRC symptoms in a primary care setting are likely to be diagnosed with CRC within the next 2 years.”

The integrated risk model has “potential to be immediately actionable in the clinical setting … [by] inform[ing] patient triage, improving early diagnostic rates and health outcomes and reducing pressure on diagnostic secondary care services.”

SOURCE:

The corresponding author is Harry D. Green of the University of Exeter, England. The study (2024 Aug 1. doi: 10.1038/s41431-024-01654-3) appeared in the European Journal of Human Genetics.

LIMITATIONS:

Limitations included an observational design and the inability of the integrated risk model to outperform FIT, which has a receiver operating characteristic area under the curve of 0.95.

DISCLOSURES:

None of the authors reported competing interests. The funding sources included the National Institute for Health and Care Research and others.

A version of this article first appeared on Medscape.com.