Lung Cancer: What Genetics Can - and Cannot Tell Us

World Lung Cancer Day | August 1

When we hear “lung cancer,” most of us immediately think of smoking. While tobacco remains the biggest risk factor, the complete picture is more complex. Lung cancer can also affect people who have never smoked.

Second-hand smoke, air pollution, workplace exposure to substances such as asbestos and diesel exhaust, chronic lung disease, and genetic susceptibility can all influence a person’s risk.

The global and Indian burden of lung cancer

Lung cancer remains the most commonly diagnosed cancer worldwide and the leading cause of cancer-related death. In 2022, nearly 2.5 million people were diagnosed with lung cancer, and more than **1.8 **million died from the disease.

India reported an estimated** 81,748** new cases and 75,031 deaths in the same year. Lung cancer was the fourth most commonly diagnosed cancer in India, but it accounted for a disproportionately high 8.2% of all cancer deaths.

These numbers tell us something important: lung cancer is still often detected late, when treatment becomes more difficult. This is why awareness, timely evaluation, and appropriate screening matter so much.

Does lung cancer run in families?

As a genetic counsellor, this is one of the most common questions I hear.

Most lung cancers are not caused by a single inherited genetic change. They usually develop because of a combination of ageing, environmental exposure, lifestyle factors, and an individual’s genetic susceptibility.

However, there are situations where an inherited risk may need to be considered. These include lung cancer diagnosed at a young age, several close relatives with lung cancer, multiple cancers in the same person, or a diagnosis in someone with little or no history of smoking.

Even then, family history needs to be interpreted carefully. If several family members have developed lung cancer, the reason may be shared genes, shared exposure to tobacco or environmental pollutants, or a combination of both.

Not all genetic tests are the same

There is often confusion between tumour testing and hereditary cancer testing.

Tumour biomarker testing examines genetic changes within the cancer cells. These changes usually develop during a person’s lifetime and may help the oncologist choose targeted therapy or immunotherapy. They are not automatically inherited or passed on to children.

Hereditary, or germline, genetic testing is different. It is usually performed using a blood or saliva sample and looks for genetic changes that a person was born with. If a clinically significant inherited variant is identified, the result may have implications for the patient as well as their biological relatives.

Sometimes, tumour testing detects a change that could potentially be inherited. In such cases, a genetic counsellor may recommend confirmatory germline testing before any conclusions are drawn about the family’s risk.

Should everyone get a genetic test?

No. Genetic testing is not a general screening test for lung cancer.

Before recommending hereditary cancer testing, a genetic counsellor reviews the person’s age at diagnosis, medical history, smoking and exposure history, tumour findings, and family history on both the mother’s and father’s sides.

Testing is useful only when it can answer a meaningful clinical question. It may also produce an uncertain result that does not clearly confirm or rule out inherited risk. This is why counselling before and after testing is so important.

It is equally important to understand that a consumer genetic-risk report or polygenic risk score cannot diagnose lung cancer, guarantee that someone will develop it, or confirm that they are safe from it.

Genetics cannot replace screening.

Genetic testing and lung cancer screening have very different roles.

For people at high risk, particularly those with a significant smoking history, low-dose CT may help detect lung cancer at an earlier stage. Screening should be discussed with a physician, as eligibility depends on factors such as age, smoking history, general health, and applicable clinical guidelines.

Anyone experiencing a persistent cough, coughing up blood, chest pain, shortness of breath, unexplained weight loss, or ongoing fatigue should seek medical advice. These symptoms do not always indicate cancer, but they should not be ignored if they continue or worsen.

What can you do today?

Start by learning your family’s cancer history. Note which relatives had cancer, what type they had, and their age at diagnosis. Information from both sides of the family is equally important.

Avoid tobacco and second-hand smoke wherever possible. Be aware of occupational and environmental exposures. If you have a significant smoking history, speak to your doctor about whether lung cancer screening is appropriate for you. If your personal or family history raises concern about inherited cancer risk, consult a qualified genetic counsellor before choosing a test.

From a genetic counsellor’s perspective, genetic information is most useful when it is interpreted in the right medical and family context. It is not about predicting the future with certainty or creating unnecessary fear. It is about helping people ask the right questions and make informed health decisions.

This World Lung Cancer Day, let us remember that lung cancer is not limited to smokers, every genetic finding is not hereditary, and no genetic test can replace timely medical care.

References

World Health Organization (WHO). Lung Cancer Fact Sheet.
International Agency for Research on Cancer (IARC). GLOBOCAN India Fact Sheet.
National Cancer Institute (NCI). Biomarker Testing for Cancer Treatment.
Centers for Disease Control and Prevention (CDC). Lung Cancer Screening.