Lung cancer is a daunting reality for millions of people across the globe, with smoking as its primary cause. However, it's crucial to recognise that lung cancer can also develop in non-smokers. How, you ask? Have you ever stood next to someone smoking? Being in close proximity to smokers, for instance, can unwittingly increase your chances of developing lung cancer. As a matter of fact, lung cancer in non-smokers is more common than we think, with 48% of people who were diagnosed with lung cancer being non-smokers.

This highlights how vital it is to educate ourselves on all aspects and risk factors behind this devastating disease, along with its resulting symptoms among those who have never lit up.

By being informed of all this information, as well as the prevention methods and treatments available, everyone can be better equipped to fight back against a common enemy - lung cancer.

What is Lung Cancer: More than Just a Smoker’s Disease

Lung cancer, characterised by the malignant growth of cells within the lungs, is a major health concern not just globally but also in Singapore. When cancer cells proliferate unchecked, they not only disrupt lung function but can also spread aggressively to nearby lymph nodes, other lung areas, and distant organs such as bones, the brain, and the liver.

Data from the Singapore Cancer Registry Annual Report 2021 highlights the prevalence of lung cancer. It ranks as the third most common cancer among Singaporean adults and poses a significant threat, particularly to the elderly population. For instance, according to the Singapore Cancer Registry Annual Report 2021, in males aged 80 and above, lung cancer is the leading cancer diagnosis, representing a substantial proportion of cancer cases in this age group. In contrast, for males between the ages of 30 and 39, lung cancer ranks as the 10th leading cancer, with only 30 cases registered. However, the incidence rises significantly with age; amongst men aged 60 to 69, the number of cases escalates to 1,765, underscoring how lung cancer prevalence increases dramatically in older populations.

Similarly, it remains a common cancer among older females, underscoring the need for awareness across all ages and genders.

What Causes Lung Cancer?

Lung cancer arises from mutations within the DNA of lung cells, causing them to proliferate uncontrollably and outlive normal cells, leading to the formation of tumours. These tumours can aggressively invade nearby tissues and, over time, may spread to other parts of the body.

The principal causes of lung cancer include:

• Smoking: The leading cause of lung cancer, smoking introduces carcinogens that damage lung cells. This risk also extends to non-smokers through exposure to secondhand smoke.
• Environmental Toxins: Exposure to substances like asbestos in shipyards and certain heavy metals like arsenic, which tend to be used in pharmaceuticals, can trigger lung cancer, even in non-smokers.
• Genetic Factors: In some cases, genetic predispositions may increase susceptibility to lung cancer, emphasising the importance of family medical history.
• Particle Pollution: Exposure to particle pollution, a mix of tiny solid and liquid particles in the air, particularly from sources like exhaust smoke, can elevate the risk of developing lung cancer.
• Chronic Inflammation: Ongoing lung inflammation from conditions like tuberculosis or chronic bronchitis can increase the risk of lung cancer.

How Smoking Leads to Lung Cancer?

As mentioned, smoking tobacco is the predominant cause of lung cancer. This high percentage is due to the carcinogenic substances in cigarette smoke, which begin to damage lung cells almost as soon as they are inhaled.

The process is twofold:

• Initial Damage: Carcinogens in smoke can cause immediate changes in lung cells. Although the body may repair some of this damage, repeated exposure can overwhelm these repair mechanisms.

• Progressive Harm: Continued exposure leads to irreversible changes in the cells, creating conditions conducive to cancer development.

Additionally, smoking can increase cancer risk by interacting with other carcinogens like radon and asbestos, magnifying the risk.

Which Substances in Cigarettes Are Linked to Cancer?

According to Cancer Research UK, there are at least 70 carcinogenic substances in tobacco smoke. These chemicals are not only hazardous but are also commonly associated with other industrial and toxic uses, highlighting their potential danger:

• 1,3-Butadiene: Commonly used in rubber manufacturing, this chemical is a significant component of cigarette smoke.
• Arsenic: Known for its use in poisons, arsenic is alarmingly present in tobacco.
• Benzene: Sourced from crude oil and used as an industrial solvent, benzene is a potent carcinogen found in cigarette smoke.
• Beryllium: Used in nuclear reactors, beryllium becomes dangerous when inhaled through cigarette smoke.
• Cadmium: Typically used in battery production, cadmium adds to the toxic profile of cigarette emissions.
• Chromium: Used to make dyes, paints, and alloys for cars, chromium contributes to the carcinogenic makeup of cigarette smoke.
• Formaldehyde: Common in science labs and mortuaries, formaldehyde is another cancer-causing agent found in cigarettes.
• Polonium-210: This intensely radioactive element elevates the health risks associated with smoking.
• Polycyclic Aromatic Hydrocarbons (PAHs): Including benzo(a)pyrene, found in coal and oil, PAHs are part of the dangerous chemical suite in tobacco smoke.

What Kinds of Lung Cancer Are Found in Individuals Who Have Never Smoked?

As mentioned above, non-smokers are also at risk for developing lung cancer. These cancers often have distinct characteristics and origins compared to those typically seen in smokers.

• Adenocarcinoma: Most common in non-smokers, it starts in the cells lining the air sacs and grows slowly.
• Squamous Cell Carcinoma: Less common in non-smokers, it affects the flat cells lining the airways and often grows centrally.
• Small Cell Lung Cancer: Though rare in non-smokers, it's aggressive and fast-growing.

Causes of Lung Cancer in People Who Do Not Smoke

A combination of environmental and genetic factors can contribute to lung cancer in individuals without a history of tobacco use.

In non-smokers, lung cancer often arises from genetic mutations within lung cells that disrupt normal cell growth and death. Environmental factors such as radon gas, secondhand smoke, and workplace carcinogens can also play a significant role in lung cancer development.

Is Lung Cancer Different in Non-Smokers Than in Smokers?

Lung cancer in non-smokers presents differently from that in smokers, not only in its origin but also in its progression and response to treatment.

Consider these factors as listed by Yale Medicine:

• Location and Appearance: Non-smokers' lung cancer usually starts at the lung's edges, often in the cells producing mucus. These cancers tend to be spread out, not forming solid lumps, making early detection harder.
• Growth Rate: Cancers found in non-smokers generally have a slower growth rate compared to those in smokers. This slower progression can affect how they respond to cancer treatment and can sometimes result in better outcomes if caught early.
• Metastatic Behaviour: While slower growing, they can still spread, but less aggressively than in smokers. Ongoing monitoring is still necessary, even after treatment.

What Are the Warning Signs of Lung Cancer?

This is why even non-smokers need to be aware of the possible signs and symptoms of lung cancer, which may include:

• Persistent coughing that worsens over time
• Chest pain
• Difficulty breathing
• Wheezing
• Coughing up blood
• Feeling constantly fatigued
• Unexplained weight loss

Lung cancer, or lung carcinoma, is often referred to as a "silent killer" because it can develop without causing noticeable symptoms in its early stages. Therefore, if you or someone you know experiences any of these symptoms, it is recommended to seek medical evaluation promptly from a lung cancer specialist in Singapore, such as OncoCare, as early detection and treatment can improve the chances of successful outcomes.

Screenings For Lung Cancer

If you are worried about lung cancer, or if you have a history of smoking or other risk factors, it is important to talk to your healthcare provider about the appropriate screening tests for you. The only recommended screening test for lung cancer is low-dose computed tomography (LDCT).

During an LDCT scan, a low dose of radiation is used to create detailed images of your lungs. The scan is painless and only takes a few minutes to complete. For non-smokers, regular testing to detect lung cancer can involve being aware of common symptoms, such as coughing, shortness of breath, and chest pain, and seeking medical attention if these symptoms persist.

In addition, regular check-ups with your healthcare provider can help detect any abnormalities or changes in lung function, which may indicate the need for further testing or evaluation.

Lung Cancer Treatment Options In Singapore

For patients diagnosed with lung cancer, treatment options depend on the stage and severity of the disease.

Early-Stage Lung Cancer:

• Surgery:
  • Lobectomy (removal of a lung section)
  • Pneumonectomy (removal of the entire lung)
• Additional Treatments:
  • Chemotherapy
  • Oral targeted therapy
  • Immunotherapy
  • Combination therapies

Advanced Lung Cancer (when surgery isn't possible):

• Radiation therapy: Uses high-energy rays to target and destroy cancer cells.
• Chemotherapy: Uses medication to stop cancer cell growth and division.
• Targeted therapy: Blocks specific cancer-promoting processes within cancer cells.
• Immunotherapy: Stimulates the body's immune system to fight cancer cells.

What Steps Can I Take to Reduce My Risk of Developing Lung Cancer?

Mitigating the risk of lung cancer requires a range of measures, especially for individuals who haven't smoked but might face other potential risk factors.

• Avoid Exposure to Harmful Substances: Stay away from secondhand smoke and limit exposure to workplace carcinogens.
• Radon Testing and Mitigation: Test your home for radon and take action to reduce levels if they're high.

Get The Help You Need 

Lung cancer in non-smoking people is a frightening and sobering reality. It is much more common than we believe and can happen to anyone.

Those with a higher risk should pay particular attention to changes in health that could potentially be related to lung cancer. As with all things health-related, being proactive and seeking care from qualified professionals is a must. If there is a history of lung cancer in your family, discuss with your doctor about your risk and any preventive measures you can take. Don’t wait until symptoms become more serious; If you feel like something seems off or you have any concerns about your lung health, please don't hesitate to book an appointment with an experienced cancer centre in Singapore.

“Expert knowledge means better care for cancer”

Written by:

Dr Tay Chee Seng

MBBS (Singapore)

MRCP (United Kingdom)