Very sorry to hear about your good friend's problems.
First, I have never heard of the Birch Ash Therapy but I'm sure that someone, somewhere, must believe in it, and secondly, I feel that I am really offering myself to plenty of ridicule and mockery by offering any kind of solution or treatment for the eternal cancer problem.
However, having said that, if the following sites can offer your friend any kind of solace or comfort, then I'll gladly put up with a few snotty remarks or name calling by those who supposedly know better.
1.
http://www.cancerfungus.com/en/
2.
http://articles.mercola.com/sites/articles/archive/2013/03/10/ketogenic-diet.aspx?e_cid=20130310_SNL_Art_1&utm_source=snl&utm_medium=email&utm_content=art1&utm_campaign=20130310
Both articles claim that cancer is a fungus. Article 1. states that it was killed (like all fungi) by bi-carbonate of soda whilst Article 2. states that the cancer fungi only feeds on pure sugar and can be starved to death.
In support of Article 2. I passed this on to my granddaughter's friend who gave up granulated and similar sugars and started the ketogenic diet for some weeks.
At a later check up on his cancer, it was found that it was shrinking and he was told by the nurse that his type of cancer have not been previously known to shrink.
I offer the above sites in the hope that your friend may find some interest, comfort and, possibly, hope for the future in the contents but that is as far as my offer can possibly go.
It would appear that the drug companies cannot make a profit with bi-carbonate of soda or out of sugar-free diets so they are not interested.
However, wasn't Aspirin (or similar) found by chewing a piece of tree bark???