What is lung cancer?

Lung cancer is also called bronchogenic carcinoma or bronchial cancer. Just like any other cancer, tumors form and spread in the lungs leading to death. In fact, lung cancer tumors form in the bronchi or parenchyma of the lungs. It affects more than one million people each year worldwide being the greatest cancer-leading cause of death in the US. At present, no systematic screening for lung cancer is available, because no method has yet been able to demonstrate its effectiveness. Lung cancer is the 4th most common cancer in France. Also, it affects more men than women (66% men and 34% women). Its incidence has been stable since 1980 in men but increasing in women due to the increase in female smoking. It can affect young people (under 40) because tobacco is sometimes initiated in adolescence.

Types of lung cancer:

Lung cancer reaches the cells of the bronchi or the cells that line the pulmonary alveoli. There are two types of lung cancer. To illustrate, they do not look the same under the microscope and do not react the same way to cancer treatments. They are:

• “Non-small cell” cancers, which are the most common (about 80% of cases). The most occuring types are adenocarcinoma, squamous cell carcinoma and large cell carcinoma.
• "Small cell” cancers which represent 15 to 20% of bronchial cancers.

What causes lung cancer?

• Smoking is the main risk factor for lung cancer. The daily consumption of tobacco in all its forms (cigarette, rolling tobacco, cigar, pipe, etc.) is responsible for approximately 8 out of 10 lung cancers. Furthermore, years of exposure is more important than the amount of tobacco smoked per day. It is therefore better to stop smoking as soon as possible to reduce the risk of cancer, rather than to reduce the amount of tobacco consumption per day. This is because smoking even very little but daily and for a long time is much more harmful than smoking a lot on a shorter period. Finally, passive smoking, that is the exposure to cigarette smoke without smoking, increases the risk of developing lung cancer by 30%.

• More rarely, occupational exposure to toxic products such as asbestos, arsenic, cobalt, nickel, or chromium, for example, is the cause. These non-tobacco-related lung cancers account for approximately 15% of cases. The risk of lung cancer increases in the event of occupational exposure to these substances and smoking.

Symptoms:

The symptoms of lung cancer are multiple and of different nature depending on whether or not it is related to smoking:

• Respiratory symptoms are present in half of the cases (persistent cough, shortness of breath, chest pain, sputum streaked with blood, frequent lung infections);
• General signs such as abnormal fatigue, loss of appetite or weight loss;
• Other less common signs such as voice change, wheezing or difficulty swallowing.

If these symptoms persist, the patient will need immediate medical attention.

Risk factors of lung cancer:

• Smoking and passive smoking
• Family history of lung cancer
• Exposure to chemical toxic substances such as asbestos, cobalts and others.
• Radiation therapy to another cancer type

How to diagnose lung cancer:

If certain symptoms raise the suspicion of lung cancer, the doctor then prescribes a series of tests to confirm or refute the diagnosis. Generally, a sputum examination is carried out in search of malignant cells by microscopy, an X-ray and a scanner of the thorax. In addition to a bronchial fibroscopy, which makes it possible to carry out a biopsy (to identify the type of cancer) and to visualize the bronchi in order to specify extension of the tumor.

Sometimes there's a need to perform transparietal puncture (using a needle through the chest wall) to take samples if the tumor is located on the periphery of the lung and is not accessible by fibroscopy. Histological diagnosis by microscopy of a fragment of tissue makes it possible to distinguish the type of lung cancer (“non-small cell” or “small cell”).

Furthermore, it's possible to identify tumor genetic mutations. Some tumors may express a genetic mutation. The search for these mutations is carried out via a biopsy of the cancer cells which is sent for analysis to a pathology laboratory. The result will make it possible to better adapt the treatment by opting for targeted therapies, the role of which is to block the growth mechanism of cancerous cells. The main genetic mutations in lung cancer are located on the KRAS, EGFR, ALK genes...

If cancer is certain:

If the diagnosis of bronchial cancer is certain, further examinations are necessary to allocate possible secondary disseminations (metastases) in the body. The doctor can then request, for instance, a bone scintigraphy, an ultrasound of the liver, an endoesophageal ultrasound, an angiography to visualize possible damage to the aorta and the pulmonary vessels, or even a mediastinoscopy to look for damage to the mediastinum lymph nodes.

How to prevent lung cancer:

• Minimize exposure to toxic chemicals at work by wearing a face mask or taking other safety measures.
• Cease smoking or never smoke to begin with.
• Avoid comming near a person who's smoking or staying a closed room with a smoker.
• Take your vitamins from natural fruits and vegetables rather than supplements.

Lung cancer teatment:

The cessation of smoking is always a prerequisite for treatment. The therapies chosen then depend on the type of bronchial cancer identified as "non-small cell" or "small cell", its stage of development and the general condition of the patient.

In “non-small cell” lung cancers, surgery is most often considered to remove the tumour. Removal of a lung lobe or the entire lung can be performed. Then chemotherapy associated or not with radiotherapy is often a treatment depending on the case.

In relatively extensive forms of cancer, chemotherapy is sometimes performed before surgery in order to reduce the tumor volume. Finally, in some very extensive forms with metastases, surgery is not applicable. A treatment combining chemotherapy, radiotherapy and targeted therapies aims to control the progression of the disease. “Small cell” lung cancer has tendency to spread very quickly in the body. Surgery is very rarely indicated in this type of cancer. In localized forms, treatment depends on chemotherapy and radiotherapy. Sometimes there's a requirement to do radiotherapy to the skull in order to prevent the appearance of brain metastases. In disseminated forms, it is also possible to combine previous treatments with targeted therapies. Finally, immunotherapy, a new treatment that stimulates the patient's immune defenses against cancer cells. The combination of this therapy with various therapeutic protocols is now important.

After the treatments, a medical follow-up will be set up, which includes control visits on average every 3 to 4 months and a chest scan every 6 months.

Complications:

• Thrombosis
• Paraneoplastic syndromes
• Fatigue
• Nausea and vomiting due to taking chemotherapy
• Anemia
• Anorexia
• Weight loss
• Neurotoxicity
• Nephrotoxicity
• Neutropenia

References:

- Siddiqui F, Vaqar S, Siddiqui AH. Lung Cancer. [Updated 2022 May 5]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. https://www.ncbi.nlm.nih.gov/books/NBK482357/#_NBK482357_pubdet_

- National center institute "Non-small cell lung cancer treatment"

- Mayo clinic "Lung cancer"