On April 18, the results of a breast cancer study widely recognized as the largest study of its kind were published online in Nature.
In the past, breast cancer has largely been viewed as one single disease, with the addition of a few different classes in recent years. However, as well as identifying several novel breast cancer driver genes, the Nature paper describes an entirely new way of classifying and categorizing the disease based on genetic profiling. Through the findings, the Cancer Research UK scientists who conducted the study now propose there are 10 distinct subtypes of breast cancer, each with their own unique set of genetic drivers.
One putative breast cancer gene identified by the Cancer Research study was the MTAP gene. Deletions in this gene are now considered to contribute to the development of breast cancer.
Up to 2,000 individual breast cancer samples had their entire DNA and RNA expression profiles analyzed for the study. A unique aspect of this analysis was that for each tumor sample examined, information on the clinical outcome of their treatment was available for the Cancer Research team to match up with the genetics they found. This led them to identifying individual subgroups with distinct clinical outcomes.
Potentially, the impact of this data could be great; it could be used for better treatment of patients using tailored individualized treatment plans. It could even mean doing away with more aggressive forms of therapies – such as radiotherapy – in the case of certain subgroups.
The team based at the Cambridge Cancer Research Institute originally set out to further understand the nature of breast cancer heterogeneity. Speaking on BBC Radio Four recently, Carlos Caldas Professor of Cancer Medicine at CRUK and lead author on the paper said of the group’s initial research aims: “We knew that breast cancer was heterogeneous but [had] no idea how heterogeneous it was.”
Caldas also explained the future implications of the research in terms of clinical practice:
“The molecular anatomy of these subtypes is completely different in the biological sense, one day we will be able to tailor a treatment to each one that is a best fit for each of the ten subtypes.”
As to whether more subtypes of the disease remain to be discovered he used an analogy inspired by geography:
“I think we’ve identified the continents…in each continent there will be rivers and mountains and cities…there will be some finer granularity within [them]. We have really grasped…the 10 major subtypes of disease in the breast and that 10 is probably a very reasonable number.”
He said of other human cancers:
“Whether there will be as many subtypes in other common human tumors remains to be seen…”
Catch the entire BBC Radio Four interview with Carlos Caldas which featured in its Monday 23 April Material World program here.