What is MSOffice/cltreq.asp?

I was quite worried about. What is MSOffice/cltreq.asp?

I saw below one which was useful

If you run a website and check out the raw access logs, you may occasionally see that some of your visitors are requesting access to a file called msoffice/cltreq.asp. This file is part of Microsoft Office Server Extensions and it is requested by visitors to your website who have enabled the "Discuss Toolbar" that works between MS Office and MS Internet Explorer to allow users to collaboratively discuss web pages.

Do I need to worry about MSOffice/cltreq.asp?

No, you can just ignore any requests for it on your web server. To eliminate the 404 errors, you can install Microsoft Office Server Extensions.