Survival curves depicting response rates for each Cox model will also be plotted to help visualize the data. As the Cox regression model assumes that the hazard ratio between any treatment and the reference group is constant, the researchers will examine whether this assumption is violated. This will be accomplished by comparing models with and without a treatment x time interaction using a likelihood ratio test. If proportionality is violated, the researchers will use restricted mean survival time analysis as suggested by Royston and Parmar (Royston and Parmar 2013). Whether an interaction is present or not, the researchers will compare the response rates at each week of treatment.