Ductal carcinoma in situ (DCIS), as the abnormal cells inside a milk duct in the breast are called, has not spread through the walls of the ducts into the nearby breast tissue, and is therefore not breast cancer yet. It’s still unclear how we can predict which people with DCIS may develop invasive breast cancer in the future, partly due to the technical challenges involved in studying single cells in affected tissue.
To address this challenge, the researchers developed a new method, called Arc-well, which can be used to look at the single cells of old, fixed tissues—a necessity when studying DCIS over many years.
“We analyzed DCIS samples up to 31 years old as well as the samples of the invasive breast cancers which developed up to 16 years after the initial DCIS diagnosis,” says Esther Lips, associate staff scientist at the Netherlands Cancer Institute. Most DCIS lesions had already acquired many genetic changes, comparable to their invasive recurrent cancers.
Lips: “In eight out of ten patients we saw that there was a specific set of genetic changes which developed into invasive breast cancer, while in two patients multiple different sets of genetic changes were associated with breast cancer progression”.
These findings indicate that most genetic changes are already present in DCIS in a very early time point. “From a methodology viewpoint, this is a huge technical improvement, and a good technique to study samples that are years to decades old. Not only for breast cancer, but also for other tumor types or even other types of diseases” says Lips.
The next step in their research is to see what makes the difference between DCIS that progresses and DCIS that remains DCIS by looking at other characteristics like gene activity, DNA-abnormalities, and the surrounding tissue of the DCIS lesion.