Dr. Pham Thi Le Quyen from the Respiratory Department of Tam Anh General Hospital in Hanoi explains that with each puff, thousands of harmful chemicals travel directly into the lungs, coming into contact with the epithelial cells of the respiratory system. Cigarettes contain 7,000 chemicals, with at least 70 classified as carcinogens by the World Health Organization (WHO), including benzopyrene, nitrosamine, formaldehyde, arsenic, and cadmium. These chemicals affect the surface cells of the respiratory tract, causing chronic inflammation, tissue damage, and cellular changes that can lead to cancer.

Dr. Quyen explains that cigarette smoke can damage genes that control the cell division cycle, such as the p53 gene, which protects cells from abnormal growth. The p53 gene can become inactive with prolonged exposure to cigarette smoke. This allows abnormal cells to multiply unchecked, leading to tumor formation. Two other genes, KRAS and EGFR, which regulate cell division and growth, can also mutate due to the chemicals in cigarettes. Mutations in these genes cause uncontrolled cell growth, a hallmark of cancer.

The damage from smoking accumulates silently over many years. A person can smoke for 10-20 years without noticing any issues, but inside their body, genetic changes accumulate, increasing their cancer risk. "The risk of death from lung cancer is 25 times higher for smokers than for non-smokers," Dr. Quyen states, adding that 10-15 years after quitting, the risk of lung cancer drops to half that of those who continue to smoke. Even for those already diagnosed with lung cancer, quitting slows disease progression, reduces the risk of death, and improves the effectiveness of treatment.

Smoking also increases the risk of stomach, pancreatic, colorectal, and bladder cancers. Harmful chemicals in cigarette smoke can be absorbed through blood vessels in the lungs, entering the circulatory system and spreading throughout the body. Smokers and former smokers should undergo regular health checkups and screenings to assess their cancer risk.

According to Dr. Quyen, low-dose CT scans are a highly accurate screening method that can detect small lung lesions early, even before symptoms appear. This method is recommended for people aged 50-80 who have smoked 20 or more pack-years, are currently smoking, or have quit within the last 15 years. Pack-years are calculated by multiplying the number of packs smoked per day by the total number of years smoked. For example, someone who has smoked one pack a day for 20 years has a 20 pack-year history.

Khue Lam