Cancerous cells are fairly diverse across individuals, or even within a single individual, and many biological treatments require precise sequencing of the tumor DNA of that individual patient to adjust and work. In some cancers, there is a nasty "Russian roulette" effect in play, where a certain treatment may be extremely efficient (in practice a cure, even though oncologists avoid that word) in people with a certain mutation and totally useless in others, even though from the macroscopic point of view, their tumors look the same.
Then, basically, each cancer, cancer cells should be sequenced, then based on the type of cell and DNA sequencing, we have a list of "tools" to deliver payload to those very cells (without delivering such payload to sane cells, ofc)?
In practice, we can only make use of some known mutations. Not just for delivering chemicals, but also for "teaching" the immune system to attack such cells, which, once it is able to recognize them, it will do vigorously.
Let's hope that this catalogue will grow until it covers at least all the typical cases.