Non-Small Cell Lung Cancer and EGFR
Micrograph showing a non-small cell lung carcinoma
Non-small Cell Lung Cancer (often referred to as NSCLC) refers to any cancer of the lung other than Small Cell Lung Carcinoma.
The most common sub types of non-small cell lung cancer are Adenocarcinoma, Squamous Cell Carcinoma, and large Cell Carcinoma.
Adenocarcinoma lung cancer accounts for about 40% of all lung cancers.
EGFR positive lung cancer is a lung cancer which tests positive for an EGFR mutation. EGFR mutations are most common in people with lung adenocarcinoma.
What is EGFR?
EGFR stands for epidermal growth factor receptor. EGFR is protein involved in the growth and division of healthy cells. For some NSCLC sufferers there is a mutation (or damage) to the gene coding for this protein which means it can be significantly over expressed. This can cause cells to grow out of control and lead to cancer.
An EGFR mutation is the most common mutation for which there are treatments available. These new treatments, which are called targeted therapies, work directly on the lung cancer cells which express the mutation. Great progress has been made in the last decade in treating EGFR lung cancer.
How common is an EGFR mutation?
Approximately 39,000 people are diagnosed with lung cancer each year in the UK. Around 10-15% of lung cancers in the UK have sensitising EGFR mutations. The proportion is much higher in some Asian countries.
An EGFR mutation is more common in women than men, and in people who have never smoked or have been light smokers (a never smoker is defined as someone who has smoked less than one hundred cigarettes in a lifetime).
These mutations are not hereditary (present at birth) but develop later in life as a part of the process of a healthy cell becoming a cancer cell.
How is an EGFR mutation identified?
It is now recommended that everyone with non-small cell lung cancer, and particularly lung adenocarcinoma, has testing for a genetic mutation. EGFR (and other driver mutations such as ALK) can be identified in two ways.
Tissue biopsy is the most common mechanism for identifying the presence of the EGFR mutation. Your consultant will retrieve a sample of tissue from your lung either via a bronchoscopy or a needle biopsy and it will be sent to a laboratory for confirmation.
Liquid biopsy is less invasive than a tissue biopsy and is becoming increasingly common. This type of biopsy requires high levels of circulating tumour DNA in the blood which in some instances is not present. The technology in this area continues to improve and in the future is likely that liquid biopsies will become a more reliable and successful mechanism for EGFR identification.
Different types of EGFR Mutation
An EGFR mutation does not refer to a single gene abnormality. Rather, there are different types of EGFR mutation which often form part of a diagnosis of EGFR positive lung cancer and which vary according to the type of mutation and its location in a gene.
The most common EGFR mutations (around 90%) are either exon 19 deletions (which means a piece of genetic material is missing) or exon 21 L858 mutations. Part of your diagnosis may include this kind of precise information about your EGFR mutation – for example ‘EGFR exon 19 deletion detected’.