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How did smoking become the leading cause of squamous cell lung cancer? Discover the surprising data behind it!
Lung cancer, as one of the cancers with the highest mortality rate in the world, involves many different histological types. Among them, squamous cell lung cancer (SCC) has received special attention due to its distinctive characteristics and close relationship with smoking. From clinical symptoms to molecular mechanisms, the association between the development of this cancer and the use of tobacco products has sparked widespread discussion in the medical community.
Squamous cell lung cancer occupies the second place among lung cancers. It mainly originates from the bronchi. Its tumor cells appear squamous in appearance, similar to epidermal cells.
Symptoms and signs
Squamous cell lung cancer shares many common symptoms with other types of lung cancer, including persistent cough, coughing up blood, chest pain, shortness of breath, and weight loss. As the tumor grows and spreads, patients may suffer from symptoms such as difficulty swallowing due to pressure on the esophagus, voice changes, or facial edema.
These symptoms are often caused by tumor invasion or compression of surrounding thoracic structures.
Causes of squamous cell lung cancer
Risk factors
Squamous cell lung cancer is closely related to a history of smoking. According to data from the Nurses' Health Study, smokers have a significantly higher relative risk of developing squamous cell lung cancer than never smokers. As the number of years of smoking increases, the risk increases significantly.
For example, people who had smoked for more than 40 years had a relative risk of nearly 22, showing the fatal impact of smoking on the development of this cancer.
Pathogenesis
Squamous cell lung cancer often originates in the center of the main bronchus and spreads to regional lymph nodes in the early stage. However, metastasis outside the chest is usually delayed in nature compared to other types of lung cancer. The development of this tumor is often accompanied by squamation or abnormal proliferation of the epithelium.
Large studies such as The Cancer Genome Atlas (TCGA) have systematically characterized the recurrent somatic mutations that drive the initiation and progression of squamous cell lung cancer.
Gene mutations and pathways
Squamous cell lung cancer is the most mutated type of tumor because smoking is a powerful mutagenic factor. Relative to many other types of lung cancer, inactivating mutations in multiple tumor suppressor genes in squamous cell lung cancer are closely related to tumor progression.
For example, the TP53 gene is mutated in 81% of cases, and gain mutations in cancer-promoting genes such as PIK3CA and NFE2L2 have also been discovered.
Recent studies have shown that four-color mRNA expression subtypes exist in squamous cell lung cancer, which may provide a basis for personalized treatment.
Diagnostic methods
Early-stage squamous cell lung cancer often has no obvious symptoms and may only be discovered incidentally during imaging examinations. As the disease progresses, when the tumors begin to obstruct the lumen of the main bronchi, patients may develop symptoms such as atelectasis or infection.
Diagnosis usually requires a lung biopsy, and in cytology testing, typically abnormal cells can be found.
Treatment options
Treatments for squamous cell lung cancer vary and depend on the stage of the cancer, its resectability, and the genetic changes acquired by the individual tumor. Treatment for early-stage squamous cell lung cancer typically involves surgery, chemotherapy, or radiation therapy, while advanced cases require systemic therapy with the goal of remission.
Immunotherapy has shown good results in non-small cell lung cancer, among which the anti-PD-1 drug nivolumab has been approved by the US medical regulatory agency for the treatment of squamous cell lung cancer.
Epidemiological status
As of 2012, squamous cell lung cancer accounts for 22.6% of all lung cancer cases. This proportion decreases year by year as smoking rates decline. Research shows that about 91% of squamous cell lung cancer is related to smoking, and the incidence rate in men is higher than in women.
So, in today's society, with the implementation of anti-smoking policies, will the incidence of squamous cell lung cancer continue to decrease?
