Why does the iTunes cache become so big?

My computer keeps on running out of space on the hard disc. I finally figured out that it is from the iTunes cache folder being more than 200gbs! Why??? I deleted it and got everything working again. Just out of curiousity I checked again a couple days later and it was already at more than 50gbs. I run all of my movies and tv shows off of iCloud so that I don't run out of room. Is there a way I can fix this from constantly happening.