I just read the article you posted...so just a word of caution, that research review is in the "this might kinda sorta have some possible promise as a carcinoprotective agent" zone but please know that is very, very far from conclusive evidence. Couple things to be aware of:
1) Publication bias - this is a problem in all of science, but it is ESPECIALLY a problem in the basic sciences. "Significant" findings are more attractive (both from the publishing scientist's perspective and the journal's perspective) so it's possible that a number of studies where kefir had no effect did not make it to publication.
(I know many non-science people who are skeptical that this could have a large effect, but as someone who works in this field and understands the probabilities at work here...if there are enough scientists looking at enough hypotheses in enough small studies, some will appear to show a "benefit" out of sheer chance. If the studies that showed a "benefit" of an agent are aggregated and published while the studies that showed "no benefit" are left in the file drawer, it appears that the agent may have a real "benefit" only because we've never published the studies where it didn't work)
2) Many of those were animal studies, not human studies. That's fine - all research has to start somewhere and animal studies have been a crucial early step in MANY important developments of science. However, there are also many historical examples of things that showed promise in animal studies which never translated the same way into humans. This is partially due to biologic differences and, in all likelihood, also due to the publication bias above (i.e. things that didn't REALLY "work" in animals but APPEARED to because of the phenomena described above were tested in humans and proven to NOT work in a more rigorous human study).
There's probably somewhat better science right now behind kefir's benefits on our gut health than there is on kefir as a carcinoprotective agent. But hey, that would be great...
All of this process-of-science stuff is not a reason to NOT drink kefir, by the way. There's no evidence (that I know of) that it would be harmful, and it's delicious (IMO) and nutritious. You could even make your protein shakes with it, they'd be extremely creamy and would taste great. I would just caution that the research review you linked is not very compelling evidence of a carcinoprotective effect...yet.