For combining effect size from several studies, meta-analysis is the accepted method. However, for binary studies based on rare events, the existing effect size measures used in meta-analysis are inefficient. In these conditions, the Peto Odds ratio (POR) has been developed as a relative effect size estimator. in case of large treatment effects or when the group ratio is not balanced, a bias occurs in POR estimates.
POR is employed to pool odds ratios. Petos method works well for rare events as it does not need corrections for zero counts. Further, POR is also employed with dichotomous events based on time-to-event analyses.
Brockhaus, A. Catharina, Ralf Bender, and Guido Skipka. “The Peto odds ratio viewed as a new effect measure.” Statistics in medicine 33.28 (2014): 4861-4874.