If you have been working with Pau d'arco for 28 years I fail to understand why you have all your facts wrong !!
Tabebuia Avellanedae which has purple to red flowers NOT pink has proven to be the most potent in many studies and the species used by herbalists wanting the best (not the least expensive)...
The type of pau d'arco tree that produces pink flowers is NOT avellanedae but
Tabebuia heptaphylla .
T. impetiginosa and T. Avellanedae are essentially one and the same...
Stating that boiling merely increases tannins is pure hogwash...many of the active compounds within pau d'arco are not very water soluble, including lapachol as well as several other quinoids.
Capsules are essentially ineffective and not recommended for someone fighting Cancer.
They can be of some use when mixed with other herbs as pau d'arco has been shown to contain compounds that will enhance the medicinal properties of other herbs but not as any great use as a lone supplement. The same goes for Essiac which can actually be purchased in capsule form...save yourself and your money... brew the tea, it may take a little more time and be a little less convenient that merely popping a pill but if you are serious about healing this will not bother you!
Tabebuia Avellanedae is much harder to find and more expensive for a reason...it works and it works the best! I am living proof ! I am interested to hear if you have healed a form of Cancer within yourself using capsules from lesser species ?