I am investigating the effect of genomic dysmethylation on cancer survival time, with data from multiple different cancers with very different survival curves.
Normally, I would split the cases into high and low dysmethylation, and do a log-rank test on the Kaplan-Meier curves. This isn't possible because for each cancer I have only 5 or so cases where methylation was measured.
However, for every cancer, I do have 100+ cases where survival time was measured, even if methylation wasn't.
Can I do a statistical test where I measure the survival times of the cases where methylation was measured against this "background" survival curve?
Is it possible for me to combine the different groups, so I get a single answer across all the different cancers?