Genetic link between breast condition and invasive breast cancer uncovered

The genetics behind how a breast condition becomes invasive breast cancer may be explained by a new study.

Gene changes in invasive breast cancer cells were also found in abnormal cell growths called ductal carcinoma in situ (DCIS), a potentially pre-cancerous breast condition, according to the study published in Cell.

The findings suggest that these genetic faults may play a role in transforming these abnormal cells into invasive breast cancer cells.

Dr Jelle Wesseling, who is leading similar work funded by Cancer Research UK and the Dutch Cancer Society to understand which women with DCIS will develop breast cancer, said the research is an important step to learn how DCIS can develop in to invasive breast cancer.

Such progression occurs in up to 3 in 10 cases of DCIS, according to the researchers.

What is DCIS?

DCIS is where some cells lining the ducts of the breast start to turn into cancer cells. 

These cells are contained inside the ducts and have not started to spread into the surrounding breast tissue.

DCIS is often detected through screening. And it’s not yet known exactly which cases of DCIS will become invasive breast cancers and need treatment, meaning some women will receive unnecessary treatment. 

Professor Nicholas Navin, senior researcher on this study from the University of Texas MD Anderson Cancer Centre, said the gene faults that determine whether DCIS becomes invasive breast cancer are poorly understood. This is because DCIS often contains only a small number of cells – making them hard to spot – with different genetic backgrounds – making them hard to treat. 

What did the study show?

The researchers analysed the genes of more than 1,200 cells from 10 patients who had DCIS that had developed into invasive breast cancer. Because these DCIS cases had gone on to invade the surrounding breast tissue, comparing the genetic similarities offers clues about the progression from DCIS to cancer, said Wesseling. 

They found that most cancer-associated genetic changes occurred in the ducts before the abnormal cells invade into the surrounding tissue. 

They also found that multiple cancer cells move together from the ducts into the surrounding breast tissue to form invasive tumours.

Wesseling stressed the need to compare the genetics of DCIS cases that progress to invasive cancer with cases that don’t progress.

“Understanding these genetic changes will be very important in working out which cases of DCIS progress to invasive cancer,” said Wesseling. “But to completely solve the puzzle of which DCIS cases need treatment, it’s essential to link this with other information such as how the immune system responds.”

He added that collaboration between research groups to work out how to identify which cases of DCIS need treatment “would save thousands of women with harmless DCIS pointless but burdensome treatment, but also effectively treat the ones with high risk DCIS.”