I am very familiar with the CoQ10 studies! The studies are of poor design and it is impossible to know what confounding factors might be in play in these reports. Still, it was interesting enough to me, for me to add CoQ10 to my repertoire of supplements several months ago. It was especially interesting because some of these women had liver mets and they disappeared on higher doses of CoQ10. I found it something to consider because I take a statin for high cholesterol and statins are known to reduce natural CoQ10 levels. The latest research even indicates that statins may slightly increase the chances of breast cancer.....hm, that would be me.
These are probably the studies you are talking about! They were the ones that caused me to add CoQ10 to my diet!
http://www.ncbi.nlm.nih.gov/pubmed/7612003
http://www.ncbi.nlm.nih.gov/pubmed/7752835
http://www.ncbi.nlm.nih.gov/pubmed/7908519
Of particular interest was the third one
http://www.ncbi.nlm.nih.gov/pubmed/7908519