His comment was off topic and didn't contribute to the discussion.

The topic of conversation at the party was the upcoming election.

He drops the topic whenever it comes up.

He dropped the topic during the meeting.

She keeps dropping the topic whenever I bring it up.

The topicalised information was presented at the beginning of the presentation.

She likes to topicalise her blog posts.

Topicalisation is a common linguistic phenomenon.

The professor topicalises the main points in his lecture.

Topicalising the issue, she brought it up during the meeting.