Effects of Screenings in Reducing Colorectal Cancer Incidence and Mortality Differ by Polygenic Risk Scores

Effectiveness of colorectal cancer screening integrating non-genetic and genetic risk: a prospective study based on UK Biobank data

OBJECTIVE

Few studies have evaluated the benefits of colorectal cancer (CRC) screening integrating both non-genetic and genetic risk factors. Here, we aimed to integrate an existing non-genetic risk model (QCancer-10) and a 139-variant polygenic risk score to evaluate the effectiveness of screening on CRC incidence and mortality.

METHODS

We applied the integrated model to calculate 10-year CRC risk for 430,908 participants in the UK Biobank, and divided the participants into low-, intermediate-, and high-risk groups. We calculated the screening-associated hazard ratios (HRs) and absolute risk reductions (ARRs) for CRC incidence and mortality according to risk stratification.

RESULTS

During a median follow-up of 11.03 years and 12.60 years, we observed 5,158 CRC cases and 1,487 CRC deaths, respectively. CRC incidence and mortality were significantly lower among screened than non-screened participants in both the intermediate- and high-risk groups [incidence: HR: 0.87, 95% confidence interval (CI): 0.81-0.94; 0.81, 0.73-0.90; mortality: 0.75, 0.64-0.87; 0.70, 0.58-0.85], which composed approximately 60% of the study population. The ARRs (95% CI) were 0.17 (0.11-0.24) and 0.43 (0.24-0.61), respectively, for CRC incidence, and 0.08 (0.05-0.11) and 0.24 (0.15-0.33), respectively, for mortality. Screening did not significantly reduce the relative or absolute risk of CRC incidence and mortality in the low-risk group. Further analysis revealed that screening was most effective for men and individuals with distal CRC among the intermediate to high-risk groups.

CONCLUSIONS

After integrating both genetic and non-genetic factors, our findings provided priority evidence of risk-stratified CRC screening and valuable insights for the rational allocation of health resources.

Association of screening status, polygenic risk score and environmental risk factors with colorectal cancer incidence and mortality risks

Whether screening can attenuate the influence of genetic risk and environmental risk factors for colorectal cancer (CRC) mortality risk remains unknown. Our study is to investigate the association of the screening history, genetic risk and environmental risk factors with CRC incidence and mortality risks using UK Biobank data. Screening history was associated with lower CRC incidence (hazard ratio [HR]: 0.63, 95% confidence interval [CI]: 0.58-0.69) and mortality risk (HR: 0.56, 95% CI: 0.49-0.63). Compared to the HRs of participants with a low genetic risk, low environmental risk and no screening history, the HRs of participants with a high genetic risk, high environmental risk and no screening history were 3.42 (95% CI: 2.76-4.24) for CRC incidence and 3.36 (95% CI: 2.48-4.56) for CRC mortality. In contrast, the HRs of participants with a high genetic risk and no screening history, but a low environmental risk, were 1.92 (95% CI: 1.55-2.36) for CRC incidence and 1.88 (95% CI: 1.39-2.53) for CRC mortality. Furthermore, the HRs of participants with a high genetic risk and a low environmental risk, but a screening history were 1.62 (95% CI: 1.15-2.28) for CRC incidence and 1.77 (95% CI: 1.08-2.89) for CRC mortality. Participants benefited more substantially from screenings for CRC mortality than for CRC incidence risk. A higher environmental risk was associated with higher risk of CRC incidence and mortality within each category of genetic risk. These findings emphasize the importance of CRC screening and identifying environmental factors to reduce CRC incidence and mortality risks.

Clinically relevant combined effect of polygenic background, rare pathogenic germline variants, and family history on colorectal cancer incidence

BACKGROUND AND AIMS

Summarised in polygenic risk scores (PRS), the effect of common, low penetrant genetic variants associated with colorectal cancer (CRC), can be used for risk stratification.

METHODS

To assess the combined impact of the PRS and other main factors on CRC risk, 163,516 individuals from the UK Biobank were stratified as follows: 1. carriers status for germline pathogenic variants (PV) in CRC susceptibility genes (APC, MLH1, MSH2, MSH6, PMS2), 2. low (< 20%), intermediate (20-80%), or high PRS (> 80%), and 3. family history (FH) of CRC. Multivariable logistic regression and Cox proportional hazards models were applied to compare odds ratios and to compute the lifetime incidence, respectively.

RESULTS

Depending on the PRS, the CRC lifetime incidence for non-carriers ranges between 6 and 22%, compared to 40% and 74% for carriers. A suspicious FH is associated with a further increase of the cumulative incidence reaching 26% for non-carriers and 98% for carriers. In non-carriers without FH, but high PRS, the CRC risk is doubled, whereas a low PRS even in the context of a FH results in a decreased risk. The full model including PRS, carrier status, and FH improved the area under the curve in risk prediction (0.704).

CONCLUSION

The findings demonstrate that CRC risks are strongly influenced by the PRS for both a sporadic and monogenic background. FH, PV, and common variants complementary contribute to CRC risk. The implementation of PRS in routine care will likely improve personalized risk stratification, which will in turn guide tailored preventive surveillance strategies in high, intermediate, and low risk groups.

Preferences for a polygenic test to estimate cancer risk in a general Australian population

PURPOSE

There is significant interest in the use of polygenic risk score (PRS) tests to improve cancer risk assessment and stratified prevention. Our current understanding of preferences regarding different aspects of this novel testing approach is limited. This study examined which attributes of a PRS test most influence the likelihood of testing.

METHODS

A discrete choice experiment was developed to elicit preferences for different aspects of a PRS test by surveying an online sample of the Australian population. Preferences were assessed using mixed logistic regression, latent class analysis, and marginal willingness to pay.

RESULTS

The 1002 surveyed respondents were more likely to choose a PRS test that was more accurate, tested for multiple cancer types, and enabled cancer risk reduction through lifestyle modification, screening, or medication. There was also a preference for testing through a primary care physician rather than online or through a genetic specialist. A test that did not impact life insurance eligibility or premiums was preferred over the one that did.

CONCLUSION

This study found that the Australian population prefer a PRS test that is highly accurate, tests for multiple cancers, has noninvasive risk reduction measures, and is performed through primary care.