Using Xfinity Stream App with Chromecast

I see that there’s an Xfinity stream app for the Roku - might just need to get me one of these - but for the time being I’m using Chromecast. This device uses apps on your phone/tablet, by pressing the “cast” button in the app. This works in Netflix, Hulu, Amazon, and Spotify. However, I don’t see a “cast” option in the Xfinity app. Am I missing this, or if it’s not there, are there plans to add this?