Considering basic evolutionary concepts of genetic adaptations. why are we still losing the battle with cancer?

Good question!: Most cancers occur in the post-reproductive period and are genetically irrelevant. The processes normally used for tissue growth and repair are involved in cancer growth, albeit the processes have gone awry in cancer. This does not address all the issues and i hope others will chime in.

See below.: Cancer is not as simple and straight forward as one might believe. There are many different types of cancer, and they all have many molecular pathways involved. There are volumes of books to teach pathologists about all the different types. There are some successes stories for specific types of cancer, but research can take many years to find a breakthrough and is very expensive.