Unsupervised Random Forest Identifies Important Genetic Prognostic Factors for Breast Cancer Survival Time

Breast cancer is one of the most prominent and deadly diseases in the world, and its prognosis varies widely based on the expression of certain genes. Identification of these genes is important for developing and interpreting clinical prognostic tests as well as furthering our understanding of breast cancer biology. We expand on prior efforts in the field toward identifying prognostic genes, by integrating powerful statistical methods.

To this end, we use an unsupervised random forest model, which allows for robust learning of non-linear gene expression/survival relationships and the ability to identify the most important genes affecting both positive and negative breast cancer prognosis. In total, 1,518 participants were considered from the METABRIC dataset, using 20,387 mRNA expression level variables and 23 clinical variables including HER2 mutation status. The top 250 & bottom 250 expressing genes and 6 clinical features were selected for the unsupervised random forest model.

Our research corroborates previous discoveries of 27 important prognostic genes while also identifying 3 genes as potentially novel prognostic factors. Based on gene ontology analysis, we additionally show that these genes have plausible connections to breast cancer biology that should be experimentally investigated.

Here, we demonstrate the utility of the unsupervised random forest model over K-means clustering for identifying important genes in breast cancer.