#Help Data extraction systematic review

I am doing Systematic Review now. But I got a problem during data extraction. They dont quite have the HR value in the papers that i sought, not all but some. And my colleague told me that we should only collect the HR values for the OS and other quantities. Now I am confused..is it really the case? Because if yes, I wont have many papers left. If no how to or what to collect. Please enlighten me. Its my first time with the SR. I was enjoying until now and I am lost all of sudden.