Related Experiment Video
Updated: Jan 25, 2026

Generating a Murine Orthotopic Metastatic Breast Cancer Model and Performing Murine Radical Mastectomy
Published on: November 29, 2018
Different statistical techniques dealing with confounding in observational research: measuring the effect of
Marissa C van Maaren1,2, Saskia le Cessie3, Luc J A Strobbe4
1Department of Research, Netherlands Comprehensive Cancer Organisation, P.O. Box 19079, 3501 DB, Utrecht, The Netherlands. m.vanmaaren@iknl.nl.
Purpose:
Propensity trimming, hierarchical modelling and instrumental variable (IV) analysis are statistical techniques dealing with confounding, cluster-related variation or confounding by severity. This study aimed to explain (dis)advantages of these techniques in estimating the effect of breast-conserving therapy (BCT) and mastectomy on 10-year distant metastasis-free survival (DMFS).
Methods:
All women diagnosed in 2005 with primary T1-2N0-1 breast cancer treated with BCT or mastectomy were selected from the Netherlands Cancer Registry. We used multivariable Cox regression to correct for confounding. Propensity trimming was used to create a more homogeneous population for which the treatment choice was not self-evident. Hospital of surgery was used as hierarchical level to handle hospital-related variation, and as IV to deal with unmeasured confounding.
Results:
Multivariable Cox regression showed higher 10-year DMFS for BCT than mastectomy [HR 0.70 (95% CI 0.60-82)]. Propensity trimming on the 10-90th and the 20-80th percentile of the propensity score distribution and hierarchical modelling showed similar HRs. IV analysis showed no significant difference between BCT and mastectomy.
Conclusion:
Unmeasured confounding is very difficult to eliminate in observational research. We cannot conclude that BCT or mastectomy has a causal relationship with 10-year DMFS. It is crucial to critically evaluate all model's assumptions, and to be careful in drawing firm conclusions.
More Related Videos
13:35Endoscopic Bilateral Nipple-sparing Mastectomy via a Single Axillary Incision with Immediate Pre-pectoral Implant-based Breast Reconstruction
Published on: May 17, 2024
06:42Optimization of Breast Biopsy and Mastectomy Sample Collection Procedures for Biobanking, Personalized Medicine, and Research Applications
Published on: September 2, 2025
Related Concept Videos
Conservation of Small Populations
Statistical Significance
Confounding in Epidemiological Studies
What is Conservation Biology?
Conserved Binding Sites
Binding sites are often located in large pockets, and if their location on a protein’s surface is unknown, it can be predicted using various approaches. The energetic method computationally...
Strategies for Assessing and Addressing Confounding
Confounding can be addressed at both the design phase of a study and through analytical methods after data...