Comfrey and cancer-causing compounds: any new info?

I researched the heck out of Comfrey a couple years ago RE: PA safety. Does anyone have any newer information on this? The last in-depth studies seem to be in '08, and while they say that "some cultivars have more PAs than others", they do not specify if one type is safe, or even SAFER. I'd really like to be able to grow Comfrey, but until we know whether or not any certain plant will be carcinogenic/blood/liver toxic, I can't in good conscience have it on my land.

Scientists and medical doctors agree that the use of Comfrey should be restricted to topical use, and should never be ingested, as it contains dangerous amounts of hepatotoxic pyrrolizidine alkaloids (PAs). Use of comfrey can, because of these PAs, lead to veno-occlusive disease (VOD). VOD can in turn lead to liver failure, and comfrey has been implicated in at least one death. In 2001, the United States Food and Drug Administration issued a warning against internal usage of herbal products containing comfrey, and eventually banned Comfrey products intended for internal use. In addition to restrictions on oral use, scientists and medical professionals recommend applying Comfrey extracts no longer than 10 days in a row, and no more than 4–6 weeks a year.

Comfrey contains excessive amounts of symphytine, a PA, the injection of the pure alkaloid of which may cause cancer in rats. The whole plant has also been shown to induce precancerous changes in rats.

I am sorry I did not see this thread before today. Honestly, I think Comfrey is darn near a food group for me. However, I realize not all people are like I am. My constitution is cold/dry/deficient and most people are "excess" in some way.

Try these links to help you decide for yourself:
http://www.toddcaldecott.com/index.php/herbs/learning-herbs/376-comfrey
http://www.comfreycentral.com/
http://medherb.com/Materia_Medica/Symphytum_-_Comfrey,_Coltsfoot,_and_Pyrrolizidine_Alkaloids.htm