Rename the coin to Curecoin.
Have a poll on the site or in the client to determine which charity will receive the donation each month.
There are several reasons why this might work better:
The coin will appeal to more people. Some people might have not been directly affected by cancer, but I can think of countless people who have encountered some kind of illness, ailment which are equally in need of curing.
Secondly if cancer is cured, cancercurecoin becomes obsolete, whereas curecoin would move onto the next thing, as there will always be something else to cure.
Thirdly, if an epidemic hit which needed drastic donation quickly, the curecoin could be routed towards that (provided users agreed to it, via poll).
Finally, the name would be easier and shorter to remember. 'Curecoin' - 'Oh, what's that?' - 'Donates transaction fees to cure things, currently cancer, but has previously donated to cure IBS, Chrons Disease, AIDS, decided via poll by the users.' - 'Wow that's something I can get behind, my dad has X disease'.
Just my 2 cents.
+1 on this
Very well thought out suggestion.