Chemosensitivity test

Chemosensitivity (comparable to antibiotic sensitivity) in bacteria describes the sensitivity of tumour cells to a chemotherapeutic agent. It is a prerequisite for the effectiveness of chemotherapy. The opposite of chemosensitivity is chemoresistance. Chemoresistance (comparable to antibiotic resistance in bacteria) is the reduced or non-responsiveness of tumour cells to a chemotherapeutic agent.

Chemosensitivity and chemoresistance are detected with the same test procedures, which are collectively referred to as chemosensitivity tests. This test procedure checks whether the living cancer cells taken from the patient survive and are capable of reproduction despite treatment with chemotherapeutic agents. If these cells show chemoresistance, there is a >95% probability that the tumour under investigation is also resistant to the tested chemotherapeutic agent. The precise prediction of these resistances is the strength of chemosensitivity tests.

If the removed cancer cells are sensitive to a chemotherapeutic agent, this indicates that the tumour is chemosensitive to the tested drug. However, the efficacy of the chemotherapeutic agent in vivo is more difficult to predict in this in vitro procedure than in the case of chemoresistance, since not all resistance mechanisms in the body can be simulated in diagnostic tests.

The CTR-Test® measures the amount of newly formed DNA as a measure of the proliferation of tumor cells. Other test methods measure the amount of ATP in the tissue sample.

The chemosensitivity tests described above can only be performed on living tumor cells. However, it is still possible to make statements about the expected chemosensitivity of the cancer cells on the basis of archived tumour tissue. In this case, molecular-based biomarkers of the respective tumour cells are considered, which are associated with a response or non-response to certain chemotherapies.

Due to the strong dependence of therapeutic efficacy on certain molecular changes, the evaluation of selected molecular-based biomarkers prior to the application of some new targeted drugs is already standard practice.

1. Kischkel et al (2017) New in vitro system to predict chemotherapeutic efficacy of drug combinations in fresh tumor samples. Peer J 5:e3030