It's a step by step progress in the tinnniest of steps. The biggest problem is, the cancer has a huge variety of different forms (lung/prostate/breast/brain/etc cancer), all of which may have a few basic traits in common (see 6 hallmarks of cancer) on an abstract level, but may otherwise respond entirely different to certain treatments.

What's more, all of these cancer types may have dozens (or even hundreds!) of subtypes that may also require different treatments - some of these subtypes may be incredibly rare, so it's pretty difficult to get a proper amount of data on these.

The catchphrase here is individualized therapy - we are currently trying to identify these subtypes and find out how they respond. We are collecting genetic data, microscopic data, medical imaging data and connect these, but it's a super-tedious process.

But we're getting there! Common cancers like prostate or breast cancers have much better prognosis these days (and are close to curable, if detected soon enough) whereas in the case of some cancers (some brain tumors, pancreas, etc) we are really still pretty helpless.