Detecting breast cancer more reliably

Breast cancer. One in ten women is confronted with this diagnosis at a certain point in her life. The chances of being healed are good if the cancer is detected at an early stage. Therefore, preventive screenings are so important. On the other hand, benign changes shown on the Xray mammogram are often falsely rated as “highly suspicious”. Then the patients must live with the stressful suspicion of having breast cancer, until a biopsy shows that it was a false alarm. Therefore, PTB, together with physicians of the Charité Berlin, have developed a measuring method that offers more certainty in differentiating between benign and malignant tumors. Fluorescence mammography using the contrast agent indocyanine green (ICG) could be used as a supplement to the standard methods and contribute to a reduction in the number of biopsies.

After being administered intravenously, ICG binds quickly and completely to plasma proteins in blood. The resulting macromolecules are too large for the small openings in the vessel walls of benign tumors. In malignant tumors, on the other hand, the blood vessel walls are much more permeable, so that dye-labeled proteins can pass through the capillary walls and accumulate in the extracellular space. They remain there for a longer period, because decomposition in the tumor tissue is disrupted.

If the time of measurement is chosen such that the ICG circulating in the blood vessels has already been washed out by the liver, then the portion of the contrast medium extravaseated into the carcinoma can be imaged.

For detection, near-infrared laser radiation is used which causes the contrast agent to become fluorescent. This fluorescent light is measured with high sensitivity. Initial patient trials confirmed that an optical mammogram produced in this way does indeed only show an increased fluorescence contrast – i.e. an increased amount of contrast agent in tumorous tissue – if the tumor is malignant.

The prospects of this method must be extensively examined in further clinical studies. Thereby, it is particularly a matter of whether the  vascular permeability can be quantitatively determined as a physiological parameter from the measured fluorescence contrast and thus be used for an improved diagnosis of breast cancer.