In a survival meta-analysis shouldn't you use HR instead of RR? I found this interesting survival meta-analysis: https://pubmed.ncbi.nlm.nih.gov/23216926/
Why do they compare OS between the different studies using RR and not HR?
Indeed the authors of this paper mention the fact that they have used this paper (https://pubmed.ncbi.nlm.nih.gov/9921604/) as a model which it seems to refer only to HRs and not RR...
Thank you!

In general, meta-analysis is performed on summary data (eg, number of deaths by group), and odds ratios or relative risk are the only measures that can be reported from such data. Patient-level data that includes time to event is required to calculate a hazard ratio. Less commonly, patient level data that includes time to event may be available, but the well-established methods for meta-analysis rely on odds ratios and relative risk.
