A new technique allows scientists to measure how efficiently cancer drugs reach their targets inside the body in real time, differentiating cells that interact with the drug from those which do not.

The findings of this study, published in Nature Communications, could help clinicians select the best course and delivery of treatment for cancer patients. A chief cause of poor treatment outcomes post-chemotherapy is the failure to reach all cancer cells in a tumor. To eliminate this problem, an accurate measurement of the drug-to-target binding capacity is required. Current techniques fail to identify which cells have been targeted by cancer drugs. Liquefied cancer biopsies give inaccurate measurements as material from different cells gets mixed together.

Researchers at the Francis Crick Institute and Imperial College London introduced a miniature fluorescent microscope to quantify and visualize drug-target engagement of individual cells within in a tumor.

They chalked the path of the chemotherapy drug doxorubicin (Adriamycin) targeting ovarian cancer cells in living mice and found a noteworthy disparity in drug-target engagement between cells within the same tumor, and between different tumors. In addition, they found that abdominal injection of doxorubicin resulted in better drug-target engagement than administering it intravenously which is the existing preferred mode of administration by clinicians.

Erik Sahai, senior author of the paper and Group Leader at the Francis Crick Institute, said, "Our findings show that in a mouse model delivery of doxorubicin through the blood does not reach all its target cells in the body, which could help explain why this chemotherapy drug is only partially effective in some cancer patients. In contrast, delivering the drug directly into the abdomen adjacent to ovarian tumors improved its target engagement, but this was still not sufficient to kill the cancer cells."