Worldwide, smoking is the most common cause for lung cancer contributing to anywhere between 80 to 90% of all lung cancer cases depending on the country. Both active smokers and those who are constantly exposed to cigarette smoke (second-hand smoke) can develop lung cancer. The cancer is of two types – small cell lung cancer where the cancer cells are small and round in shape, while in non-small-cell lung cancer, the cancer cells are larger and oblong.
The risk comes from the following reasons:
- Cigarettes are made of over 7000 harmful chemicals, out of which over 70 are carcinogenic, or cancer-causing.
- Further, the way cigarettes are made and the chemicals used have also evolved over the years. As a result, more people are dying from cigarettes or developing lung cancer, compared to the 1950s or 60s.
- Cigarettes contain nicotine which is addictive, so frequent smokers find it very difficult to quit.
- A family history of smoking or lung cancer
Types of tobacco use/abuse
Tobacco use is a popular indulgence and has a history of over 12300 years. In the modern world, it is used or abused in the following ways:
- Chewing tobacco leaves, which is popular in rural Asia, Africa and Latin-America
- Chewing, and swallowing mouth-fresheners laced with plenty of tobacco (called ghutka in India)
The above 2 types increase the risk of oral and other cancers, but not lung cancer
- Smoking cigarettes – the most common option
- Smoking cigars and cheroots which are thicker and pack more tobacco
- Smoking cigarillos, beedis and kreteks which are thin rolls containing coarse tobacco powder
- Smoking loose tobacco powder using different types of pipe
- Non-smoking tobacco such as snuff which involves stuffing the nose with a tobacco-based product
The Connection
So what exactly is the connection? Why does tobacco consumption increase the risk of cancer? To understand this, we need to understand the structure of the lungs. The lungs are responsible for transporting oxygen that is taken from inhaled air, in to, and carbon-di-oxide out of – the tissues and cells of the body. Tiny air-sacs called alveoli present throughout the lungs are exactly where the exchange of gas between the blood and the lungs happen.
The inhaled air can contain dust, smoke, water vapor and innumerable toxins, pollutants or contaminants. There are tiny cilia or hair-like particles which act like a brush in the airways to trap these particles and expel them when we exhale, cough or sneeze.
Tobacco smoke affects lungs in the following 5 ways, primarily:
- Damage to the Alveoli: The alveoli are delicate and start getting damaged gradually from tar or nicotine deposits in tobacco. If the smoking is mild or the person quits over time, the alveoli are slowly regenerated. Else, the damage is permanent leading to a condition called emphysema, which causes shortness of breath even when one is passive.
- Damage to the Cilia: Over time, the cilia get damaged and dysfunctional from all the chemicals coming in through tobacco products. Filtering no longer happens efficiently and effectively which increases the risk of infection.
- Airway inflammation: The airways and lungs get inflamed with time, and develop scar tissue, both of which make breathing difficult for the person. Ineffective breathing means less oxygen available to the body, and hence more likelihood of disease.
- Cell behavior: The chemicals in tobacco products damage the DNA which carry the blueprint for how cells grow, multiply and behave. For example, benzo[a]pyrene (BaP) damages a part of the DNA which protects body cells against cancer. The DNA goes through unhealthy mutations including uncontrolled growth which can eventually form a tumor.
- Chemicals sticking to DNA: The unhealthy DNA mutations are also caused by toxic chemicals that start sticking to the DNA. For example, chromium present in tobacco products causes other toxic chemicals to stick to DNA, which increases the risk of cancer.
Other cancers caused by tobacco
Tobacco products are toxic enough to cause cancer in various parts of the body such as:
- Mouth
- Pharynx (throat)
- Larynx (voice box)
- Esophagus
- Stomach
- Kidney
- Liver
- Cervix
- Pancreas
- Bladder
- Colon/rectum
- Increases the risk of a type of cancer called – acute myeloid leukemia
People who do not smoke are at much reduced risk of any of these cancers.
Other lung conditions impacted by tobacco
Tobacco not only causes lung cancer but a host of other lung conditions, or it can worsen already existing lung-conditions.
- Chronic bronchitis: Frequent smokers suffer from this condition in which the airways become inflamed (swollen), eventually blocked by scar tissue and mucus. This causes frequent coughing (called smokers’ cough) and bad lung-infections such as pneumonia. There is no cure for this condition but quitting smoking can prevent further damage and also reduce symptoms compared to the past.
- Emphysema: There are thin walls that separate the tiny alveoli. Toxins in tobacco smoke start breaking down these walls. In the process, larger but fewer sacs are created. This reduces the quantity of oxygen entering the blood, eventually causing the alveoli also to break-down or get destroyed. The person reaches a point where he/she is short of breath even while resting or inactive, and will require an oxygen mask or tube to breathe, in later days. Again, the condition is not curable but quitting smoking can slow down progression of the disease and improve treatment outcomes.
- Chronic Obstructive Pulmonary Disease (COPD): In this condition, the person has both the above conditions – chronic bronchitis and emphysema. It becomes increasingly hard for the lungs to transport oxygen to the rest of the body. The person suffers from shortness of breath even while resting, coughs up mucous frequently and there are whistling, wheezing, or rattling noises when the person breathes. If the person quits smoking, COPD can be slowed down and treated better. However, the combination of COPD and lung cancer is generally fatal.
- Others: Symptoms of asthma and tuberculosis worsen if the person is a smoker.
Cardiovascular conditions impacted by tobacco
Tobacco can worsen conditions such as coronary heart disease (CHD), heart attacks, strokes, peripheral arterial disease (PAD), aortic aneurysm and peripheral vascular disease or (PVD), that are already existing.
Others conditions
Other than the above, tobacco can adversely impact
- Oral health (tooth loss, gum disease, stained teeth and bad breath)
- Sexual health (erectile dysfunction, infertility and in women, the risk of ectopic pregnancy, premature births, still-births and birth defects
- Skeleto-muscular system (rheumatoid arthritis, thin bones and hence fractures)
- Eyes (cataracts and macular degeneration)
- Immune system: more infections such as cold and flu, wounds taking longer to heal
- Sensation: reduced sense of taste and smell
- Diabetes: increased risk of type-2 diabetes
Treatment for lung cancer
Quitting smoking is the first step in the treatment for lung cancer caused by tobacco. The person may be recommended treatment at a de-addiction centers if quitting smoking is becoming difficult. Else, de-addiction medication are prescribed if the person is undergoing treatment at home. Depending on the stage of lung cancer, oral medication, chemotherapy, radiation or surgery are the various options available. Rehabilitation involves stress-management techniques such as yoga, meditation and hobbies.
Quitting smoking
Quitting smoking has a positive effect on reducing the risk of cancer in lungs and other parts of the body. This has been well-documented by agencies such as CDC and non-governmental organizations such as the American Cancer Society.
According to the CDC:
- 5-10 years of quitting: chances of developing cancer of the mouth, pharynx or larynx drops by 50 percent.
- 10 years of quitting: chances of developing cancers of the esophagus, kidney and bladder reduces.
- 10-15 years of quitting: the risk of developing lung cancer drops by 50 percent.
- 20 years of quitting: The risk of developing cancers of the mouth, pharynx, larynx or pancreas drops as much as that of a non-smoker. The risk of cervical cancer drops by nearly 50 percent.
Reviewed by Dr Suresh S Venkita, Group Medical Director, Kauvery Hospitals
Kauvery Hospital is globally known for its multidisciplinary services at all its Centers of Excellence, and for its comprehensive, Avant-Grade technology, especially in diagnostics and remedial care in heart diseases, transplantation, vascular and neurosciences medicine. Located in the heart of Trichy (Tennur, Royal Road and Alexandria Road (Cantonment), Chennai, Hosur, Salem, Tirunelveli and Bengaluru, the hospital also renders adult and pediatric trauma care.
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