Insulin-like growth factor-1, insulin-like growth factor-binding protein-3, and breast cancer risk: observational and Mendelian randomization analyses with ∼430 000 women.

N Murphy, A Knuppel, N Papadimitriou, R M Martin, K K Tsilidis, K Smith-Byrne, G Fensom, A Perez-Cornago, R C Travis, T J Key, M J Gunter

Journal: Annals of oncology : official journal of the European Society for Medical Oncology 2021;31(5):641-649

PMID: 32169310

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Abstract

BACKGROUND

Epidemiological evidence supports a positive association between circulating insulin-like growth factor-1 (IGF-1) concentrations and breast cancer risk, but both the magnitude and causality of this relationship are uncertain. We conducted observational analyses with adjustment for regression dilution bias, and Mendelian randomization (MR) analyses allowed for causal inference.

PATIENTS AND METHODS

We investigated the associations between circulating IGF-1 concentrations and incident breast cancer risk in 206 263 women in the UK Biobank. Multivariable hazard ratios (HRs) and 95% confidence intervals (CI) were estimated using Cox proportional hazards models. HRs were corrected for regression dilution using repeat IGF-1 measures available in a subsample of 6711 women. For the MR analyses, genetic variants associated with circulating IGF-1 and IGF-binding protein-3 (IGFBP-3) levels were identified and their association with breast cancer was examined with two-sample MR methods using genome-wide data from 122 977 cases and 105 974 controls.

RESULTS

In the UK Biobank, after a median follow-up of 7.1 years, 4360 incident breast cancer cases occurred. In the multivariable-adjusted models corrected for regression dilution, higher IGF-1 concentrations were associated with a greater risk of breast cancer (HR per 5 nmol/l increment of IGF-1 = 1.11, 95% CI = 1.07-1.16). Similar positive associations were found by follow-up time, menopausal status, body mass index, and other risk factors. In the MR analyses, a 5 nmol/l increment in genetically-predicted IGF-1 concentration was associated with a greater breast cancer risk (odds ratio = 1.05, 95% CI = 1.01-1.10; P = 0.02), with a similar effect estimate for estrogen-positive (ER) tumours, but no effect found for estrogen-negative (ER) tumours. Genetically-predicted IGFBP-3 concentrations were not associated with breast cancer risk (odds ratio per 1-standard deviation increment = 1.00, 95% CI = 0.97-1.04; P = 0.98).

CONCLUSION

Our results support a probable causal relationship between circulating IGF-1 concentrations and breast cancer, suggesting that interventions targeting the IGF pathway may be beneficial in preventing breast tumorigenesis.

Address: Section of Nutrition and Metabolism, International Agency for Research on Cancer, Lyon, France. Electronic address: [email protected].; Cancer Epidemiology Unit, Nuffield Department of Population Health, University of Oxford, Oxford, UK.; Section of Nutrition and Metabolism, International Agency for Research on Cancer, Lyon, France.; MRC Integrative Epidemiology Unit (IEU), Population Health Sciences, Bristol Medical School, University of Bristol, Bristol, UK; Bristol Medical School, Department of Population Health Sciences, University of Bristol, Bristol, UK; National Institute for Health Research (NIHR) Bristol Biomedical Research Centre, University Hospitals Bristol NHS Foundation Trust and the University of Bristol, Bristol, UK.; Department of Hygiene and Epidemiology, University of Ioannina School of Medicine, Ioannina, Greece; Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, London, UK.; Genetic Epidemiology Group, International Agency for Research on Cancer, Lyon, France.

DOI: 10.1016/j.annonc.2020.01.066