Allow to use original $variables['topics'] data in TMEMENAME_preprocess_forums

I need to add additional columns to topics list table such as topic views count, las. So I can override ForumManager service and extend it. I replaced getTopics function in my implementation and added additional columns. But I can't render this columns because template_preprocess_forums() function replace data from $variables['topics'] with rendered markup array, so I can't access to added columns in my THEMENAME_preprocess_forums().