Abstract: Cancerous tumours vary significantly in their response to chemotherapy agents. Currently, it is difficult to reliably assess the level of tumour responsiveness to a chemotherapy regimen during or post-administration. Biomarkers of tumour sensitivity to chemotherapy agents have hitherto been unknown. Such a biomarker would expedite identification of nonresponsive patients, who may then switch to other, possibly more effective regimens. The present invention provides a method for determining tumour responsiveness to a chemotherapy agent, wherein RNA is isolated from tumour cells of a patient before, during, and after chemotherapy. The quality of the RNA can be determined by capillary electrophoresis and assignment of an RNA integrity number (RIN). RIN values during and/or after chemotherapy are inversely proportionate to the level of tumour responsiveness. The tumour RIN is an easily accessed biomarker of tumour responsiveness to chemotherapy.