Drugs like SUTENT and GLEEVEC are CYTOSTATIC anti-cancer drugs.
The name "chemotherapy" is usually resevered for CYTOTOXIC drugs that interfere either with DNA replication or microtubule formation. These drugs do not work for GIST, have been tried many times, and never work.
Gleevec and Sutent are TARGETED THERAPIES, targeting the mutated KIT receptors on the cell surface that is sending false signals to the nucleus of the tumour cells to divide inappropriately in GIST.
These TARGETED THERPIES stop the mutated receptors causing the false signals to be sent. However, there are other targeted therapies that interfere with other links in the molecular signalling chain between cell surface and nuclues (like BRaf and MEK), so I am grossly simplifying. Better explanations lie in our website.
CHEMOTHERAPY DRUGS specifically interfere with DNA replication, so chemotherapy affects all dividing cells - not just the cancer but also those giving rise to hair growth, intestinal lining, blood cell creation in bone marrow etc. For example, HIPEC (heated intraperitoneal chemotherapy)is chemotherapy.
GIST is a sarcoma, which is a class of very rare cancers which arise from connective tissues and behave very differently to carcionomas (the usual type of cancers).
GISTs do not respond to radiotherapy, nor to chemotherapy. GIST cells do not respond to chemotherapy at all.