Colorectal cancer: why is the diagnosis of RAS important?

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The Colorectal cancer is one of the most frequent in Spain, ahead of other more known as the breast cancer. In our country each year 44,000 new cases are diagnosed, 25 percent in a metastatic state; that is, the cancer has spread to other areas of the body. However, although the figures are high, the evolution in diagnostic techniques and treatments are getting that the cure rates are increasingly higher.

One of the factors that are contributing to this revolution in therapies is precision medicine, formerly known as personalized medicine.. “It is a new approach in which the decisions of treatment and management of patients are based on the study of genes or molecules. Depending on the alterations that we find, we will indicate some drugs or others, “explains Federico Rojo, head of the Pathological Anatomy Service at the Fundación Jiménez Díaz University Hospital, in Madrid. “This will allow us to optimize the effectiveness of the drugs and avoid treating those patients that we know will not benefit”.

In the case of metastatic colorectal cancer (mCRC), the turning point in the treatment within this precision medicine has been marked by the study of alterations in RAS genes. But how does the RAS gene act in this disease? Rojo explains that this gene was described more than 30 years ago associated with different types of tumors, but the importance of RAS is that since 10 years ago the study of this gene can be used as a marker to indicate a specific therapy for patients. with metastatic colon cancer. This therapy is the use of antibodies against another gene called EGFR.

“Those people who have mCRC should study the mutation of the alteration of this gene to determine whether they can receive this drug or not. Patients who have the mutation do not benefit; Patients who do not have the mutation will benefit“, Specifies the specialist.

Approximately 50 percent of patients would benefit if they do not have this RAS mutation, which means that in these cases anti-EGFR antibodies will dramatically improve patient survival.

How is the diagnosis of RAS made?

Precision medicine represents a revolution and a paradigm shift in how medicine is approached, in this case in the treatment of CCRm, based on the study of gene alterations.

The main difference between precision medicine and traditional treatments against cancer, specifically chemotherapy, is that in metastatic colon cancer the diagnosis of RAS allows the use of biological drugs that are directed against specific molecules or factors within the tumor, while “classic chemotherapy is used indiscriminately, that is, we give all patients the same treatment regardless of the type of tumor they have,” explains Rojo.

When selecting the type of treatment required by the patient with advanced disease, the oncologist will ask the laboratory to determine if there is such an alteration or not of RAS to make a decision. As specified by the chief of the Pathological Anatomy Service at the Fundación Jiménez Díaz University Hospital, classically, the biopsy of the tumor or tumor tissue that was available. “In the last two / three years we are using much more sophisticated techniques and tools that are allowing us study these genes and alterations in mCRC from blood samples, what we know as liquid biopsy“, Add.

The advantages of liquid biopsy are many: it is a more precise technique, quicker in the response and is harmless and not annoying for the patient. The result is obtained with a blood tube. “It establishes the state of that RAS gene (if it is altered or not) at the time of making the decision and not on a diagnosis many years ago in which the disease may have changed,” emphasizes Rojo. The expert adds that it is important that the staff is trained in these innovative techniques and that the technical capacity of the laboratories and the infrastructures are adequate for the diagnosis to have quality and the doctor is safe with the decision he makes about the treatment.


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