Studies have shown that cancer cells respond differently to chemotherapy when they are grown in 2D (in a petri dish as is what happens with ChemoFx) v. 3D (as a structured tumor as is what happens in an Avatar). Some chemotherapies that are not active against cells grown in a dish are active against cells grown as a tumor, and vice versa. It is thought that 3D tumors grown respond more like the tumors in the human body. The Avatar study will help better understand this. Although ChemoFx is commercially available, the American Society of Clinical Oncology has reviewed the data and experts have come to the conclusion that these tests should not be used in general clinical practice and further investigation is needed in a clinical trial setting. I have not used this test in my practice.