Nearly 20% of people diagnosed with lung cancer have never smoked a single cigarette. How is that possible? The answer may lie in your DNA.

While smoking remains the leading cause of lung cancer worldwide, researchers have discovered that genetics also plays a significant role in determining who gets the disease. If you have a parent, brother, or sister who has had lung cancer, your risk is two to three times higher than that of someone without a family history of the condition.

Before we dive deeper, let’s take a moment to understand how genetics works. Genes are small sections of your DNA that carry instructions for how your body functions. They influence everything from eye and skin colour to how your cells grow, divide, and die.

When these genetic instructions change, due to inherited mutations or damage over time, they can disrupt the normal cell life cycle. Instead of repairing itself or dying when damaged, the cell may start dividing uncontrollably. This uncontrolled growth is the foundation of cancer, including lung cancer.

Not all genetic changes, however, carry the same risk. Some mutations are inherited from your parents, meaning they are present from birth and can increase your lifetime susceptibility to lung cancer. Others are acquired during a person’s life due to environmental exposures, such as air pollution or secondhand smoke. It’s the combination of inherited and acquired genetic changes that often determines whether lung cells grow out of control.

Researchers have identified several genes that are particularly important in lung cancer. These genes normally help control cell growth, repair DNA damage, and signal damaged cells to die. When mutations occur in these genes, the safeguards fail, and cells may begin dividing uncontrollably. Some of the most studied genes include EGFR, TP53, BRCA2, CHEK2, and ATM. Understanding how these genes work—and how their mutations affect cancer risk—can help doctors identify high-risk individuals, guide early detection strategies, and tailor treatments to the specific genetic profile of a patient’s tumour.

Having a close relative with lung cancer—such as a parent, sibling, or child—can significantly increase your own risk of developing the disease. 

However, family history is just one piece of the puzzle. Risk is highest when multiple relatives are affected, when lung cancer occurs at a younger age (before 50), or when relatives have multiple types of cancer. These patterns can indicate the presence of inherited mutations that may run in families.

Even if you have a family history of lung cancer or carry inherited genetic mutations, there are steps you can take to reduce your risk and detect the disease early. Awareness, preventive measures, regular screenings, and genetic counselling can all help you manage your risk effectively.

Understanding hereditary risk empowers you to make informed decisions, take early action, and work closely with healthcare professionals. Genetics may influence your risk, but your choices and proactive care can make a life-saving difference.