Unlike chemotherapy, which is a more generally applied treatment, targeted therapies are highly specific to an anomaly at the origin of tumor development. This is either a molecular anomaly (mutation in the tumor, and most often not hereditary) or a specific mechanism of tumor cell development. These are examples of what is referred to as "precision medicine" or "precision therapy".
These therapies are mainly administered orally
but also for some by injection (intravenous or subcutaneously).
The multiplication of tumor cells is governed by different successive stages.
These stages are driven by the action of signals from outside the cell (known as growth factors)
that trigger a ‘chain reaction’ on the surface and then inside the cell.
This chain reaction leads to the division into two new cells, and then four, and so on. Targeted therapies are designed to arrest this cell proliferation.
Targeted therapies can act at different levels :
By preventing the attachment
of this growth factor to the cell surface
One of the mechanisms by which some cancers develop is called tumor neoangiogenesis.
This is where the tumor makes its own blood vessels.
These vessels enable vascularization of the tumor necessary
for its growth but also the dissemination of tumor cells into the bloodstream.
Anti-angiogenic (blood vessel growth prevention) treatments, either as monoclonal antibodies
to Vascular Endothelial Growth Factor (VEGF) or inhibitors of VEGF receptors, work to prevent the formation of these blood vessels.
Although targeted, these drugs can nonetheless be toxic to healthy cells when the target cells are significantly similar to the normal cells. In such instances, the side effects can vary.
Most often, these side effects are early, occurring within the first weeks of treatment. They are often easily controlled by simple symptomatic treatments but may require adjustment or suspension of future dosages.
Targeted therapies often require specific research on behalf of each patient to determine the targeted tumor abnormality.
This can be a tissue biopsy or a surgical specimen after surgery and is part of the continuing advancement of personalized medicine.
Certain targeted therapies, in particular anti-angiogenics, are presently limited
to certain tumor types where the vascularization process is identified as crucial to the tumor development.