Hello
I am new to R, and I already need some help. So bear with me.

My research is about predicting response of treatment in patients with pancreatic cancer using cancer biomarkers. For each biomarker, I have created a ROC curve using the pROC package to see have well the biomarker performance (sensitivity, specificity etc.)

However, I want to combine the ROC curves of two biomarkers, to see how well they perform together.
My question is: How do I combine the two ROC curves (CA199 and VICM) into one single ROC curve in one plot?

It is my first post, so if you need more information just tell me.