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Representative sampling method improves the genetic testing for cancer treatment

A wholistic tumour sampling method developed by researchers from The Francis Crick Institute, Roche, and The Royal Marsden NHS Foundation Trust has been found to detect genetic alterations more accurately in tumours.

To aid in precision oncology, doctors can get a sample from their patient’s tumour DNA sequences to help find mutations that make the tumour more susceptible or resistant to a specific treatment. However, the genetics of tumours are complex because they are made up of different groups of cells. These often have genetic variation and sit in different locations within the tumour, meaning that current sampling methods can miss some of the genetic diversity by only using tissue taken from one small location in the tumour.

In current routine practice, only five per one million cells from a tumour are tested, meaning that clinicians are making decisions based on potentially incomplete information which could lead to patients missing out on therapies that would give them the highest chances of survival.

The concept of improved sampling was originally tested in lung and bladder cancers, where a simulation showed that this method could reduce misclassification rates in deciding whether a patient was suitable for immunotherapy from 20% to 2%, and 52% to 4% respectively when compared to current methods.

Building on this, a technique called representative sequencing was developed to give a more accurate picture of a tumour’s DNA. It takes most of the tumour removed by surgery, which in current practice is not sampled and discarded, and mix it so the cells are more evenly distributed. The researchers tested this method on 12 patients with kidney, breast, lung, colon, or skin cancer and compared the new and current methods. They found that representative sequencing gave more consistent results and can capture information from a more representative sample of the whole tumour.

The method was published in Cell Reports last week and is being further tested in 500 tumours at The Royal Marsden in London to establish its utility. A video created by Roche to describe the process can be found here: