Lung cancer is one of the most frequent cancers in Western countries and one of those that produces the highest mortality, both in men and women. There are several types of lung cancer, and the prognosis and treatment are very different between them.
What types of lung cancer are there?
The most common lung cancers are:
Squamous cell carcinoma. It is one of the most frequent in smokers. It accounts for approximately 20% of lung cancers.
adenocarcinoma. It is as common as squamous cell carcinoma but appears in both smokers and non-smokers; in fact it is the most common in non-smokers. It accounts for approximately 35% of lung cancers.
Small cell carcinoma (oat cell). It is a tumor that spreads very quickly to other locations (metastasizes), so when it is diagnosed, it is assumed that it has already spread outside the lung. It represents between 10 and 15% of lung cancers. It appears almost exclusively in smokers.
Large cell carcinoma. It only accounts for 5% of all lung cancers.
Other cancers. There are other rarer tumors whose prognosis is very different depending on their type. The lung is also a common site where other tumors spread (metastasize).
Causes of lung cancer
Most lung cancers are associated with tobacco use or exposure to secondhand smoke. However, there are people who smoke and never develop cancer and, conversely, people who have lung cancer and have never smoked. In fact, between 10% and 15% of lung cancers appear in people who have never smoked. Other environmental and toxic factors can also favor the appearance of lung cancer, such as radiation. People who have received radiation therapy for any reason (for example, having had another cancer) are more likely to later develop lung cancer.
There is also a certain genetic predisposition for some of them, these cancers being more frequent in some families than in others.
Symptoms associated with this type of cancer
The clinic produced by lung cancers is very varied:
Some patients are asymptomatic and the cancer is discovered incidentally when they have a chest x-ray for some other reason.
In most cases it produces symptoms related to the lung, the most frequent being cough, accompanied or not by expectoration, sometimes with blood, chest pain and difficulty breathing.
In some patients, cancer is discovered after verifying that what was thought to be pneumonia is not completely cured, and what is really underneath is cancer. It can also be discovered during the study of a pleural effusion.
In other patients it is discovered while performing a study due to unexplained weight loss, fatigue or loss of appetite.
Some lung cancers produce hormone-like substances that give rise to very diverse metabolic alterations (low sodium, high calcium, Cushing’s syndrome, etc.).
Lung tumors frequently metastasize (spread to other organs), and metastases may be the first sign of the disease. Metastases can reach almost any organ, including the brain (headache and loss of strength on one side of the body), bones (pain and fractures), bone marrow (anemia), liver (pain and yellow discoloration), and They can promote the growth of nodes in abnormal sites.
How is the diagnosis of the disease made?
The initial diagnosis of suspected lung cancers is made by chest x-ray. Squamous cell carcinoma and small cell carcinoma are usually seen as large masses in the central zone of the lung, whereas adenocarcinoma and large cell carcinoma usually affect the peripheral zone of the lung, sometimes with involvement of the pleura. Confirmation that there is a tumor, its size, its characteristics and the degree of local extension is done by means of a CT scan of the chest.
Definitive confirmation of the type of tumor is established with a lung biopsy obtained by fiberoptic bronchoscopy or by puncture of the mass through the skin (FNA) and guided by CT. Sometimes the diagnosis is established by taking a biopsy of a node that is affected and that can be found under the skin or in the mediastinum, in the latter case by performing a mediastinoscopy. Diagnosis can also be made when a pleural effusion is present by looking for malignant cells in the effusion fluid obtained by thoracentesis.
In lung cancers it is necessary to know its extension. To do this, a CT scan of the whole body, a bone scan and/or a bone marrow puncture are usually performed to assess the presence of metastases.
About 10% of non-small cell lung cancers may have an associated mutation in their cells, such as a mutation in the epidermal growth factor receptor (EGFR) or the ALK oncogene. This mutation must always be evaluated when obtaining tumor tissue after a biopsy or FNA, since it modifies the type of treatment.
Can lung cancer be prevented?
Obviously the best way to reduce the chances of getting lung cancer is not to smoke.
Various studies have evaluated whether systematically performing chest X-rays or chest CT scans in smokers could detect the presence of lung cancers in early stages that would allow them to be cured. While most cancers are indeed detected in early stages, many non-malignant lesions are also discovered on which many interventions, including surgery, are performed, which are expensive and can have fatal complications. There are conflicting results about whether early cancer detection actually reduces the number of deaths at a reasonable cost. The recommendations of the American Preventive Services suggest performing an annual low-intensity CT scan on subjects between 55 and 80 years of age who currently smoke or who have quit tobacco less than 15 years ago, who have consumed at least the equivalent of 1 pack of cigarettes a day for 30 years (10 cigarettes a day for 60 years or 2 packs a day for 15 years) and who are in good enough health to have lung surgery if cancer is diagnosed.
Is it hereditary?
Some lung cancers are more common in people from the same family, although there is no clear pattern of inheritance from parents to children.
What is the prognosis for lung cancer?
The prognosis depends on the type of lung cancer, its extension and the patient’s health situation, fundamentally on whether their physical situation allows the most appropriate treatment to be applied. The latter is important when deciding if surgery can be performed, since although the tumor could be removed, it is always at the expense of removing part of the lung. In some people with a pulmonary situation already at the limit, for example patients with COPD, perhaps nothing can be removed from the lung anymore because it is incompatible with maintaining a minimum subsequent respiratory capacity.
In general, lung cancer is one of the most serious cancers, with a survival rate of approximately 15-20% 5 years after diagnosis. The evaluation of the extension differs depending on the type of tumor:
Non-small cell lung cancer. It is classified in stages from I to IV depending on the characteristics of the tumor in terms of its local extension (T), lymph node involvement (N) or the presence of metastases (M).
Stage I. There are no nodes (N0) or metastasis (M0). It is subdivided into IA or IB depending on the size of the tumor and its location within the lung.
Stage II. It implies a more advanced local involvement, either due to the existence of nearby lymph nodes (IIA) or because the tumor affects the pleura, the diaphragm or the main bronchus (IIB).
Stage III. It implies involvement of neighboring organs by the tumor (IIIB) or extensive local extension along with lymph nodes (IIIA).
Stage IV. There are metastases (M1).
Small cell lung cancer. It’s divided in:
Located. It affects a single lung with or without local lymph node involvement. More than 20-25% of patients live more than 5 years.
Extended. It affects some other part of the body or the other lung. Survival is lower than in localized cancer.
For this classification it is necessary to perform a CT scan of the entire body and a gammagraphy of the bones. Sometimes a puncture of the bone marrow and a CT of the brain are also performed, which rule out that the tumor has spread to these locations. PET can also be used to study lung extension and the presence of metastases.
The diagnosis of the extension is essential when making decisions about the most appropriate treatment, so it is often necessary to carry out tests, even aggressive ones, to confirm or not the involvement of lymph nodes in a certain place or the presence of metastases.
What is the treatment of the disease?
Traditionally, the treatment of lung cancer has been divided according to whether it was a small cell carcinoma or a non-small cell carcinoma.
In small cell carcinoma, it is accepted that the tumor is already widespread at the time of diagnosis and treatment is based on chemotherapy and frequently, if the tumor does not seem to be very widespread, associated radiotherapy at the same time. Only in very specific situations, in cancers detected in very early stages, can surgery be recommended, subsequently associating chemotherapy, with or without radiotherapy. In many patients, the initial response to chemotherapy is good, with a significant percentage achieving complete regression of the disease. In general, several medicines are combined, more or less strong depending on the clinical situation of the patient. Sometimes preventive brain radiation therapy is given, in case there are cancer cells in the brain where chemotherapy may not reach. This type of radiation therapy reduces the chances of developing brain metastases in the future. Chemotherapy is usually given in cycles of 1 to 3 days in length and every 3 weeks. In general, between 4 and 6 cycles are administered.
In non-small cell cancers, the treatment would be, if possible, surgery or curative radiotherapy. With a few exceptions, in order to be able to operate on the tumor it must be localized (that is, it must not have produced metastasis, there must be no pleural effusion with malignant cells, there must be no involvement of neighboring organs, no involvement of the other lung, or involvement of lymph nodes in distant territories, etc.) and the patient must have good enough physical and pulmonary capacity to be able to breathe properly after removing the part of the lung where the cancer is located and to withstand the operation. To assess these aspects, a spirometry is performed to indicate the patient’s lung capacity.
In stages I and II, and in some in stage III, surgery is performed. A lung lobe is usually removed and the prognosis can be good, with survival rates greater than 50% at 5 years after the operation. Some patients who do not want or cannot undergo surgery receive radiotherapy with curative intent, although the success rate is lower than that of surgery. Radiation therapy may also be given after surgery if all of the tumor has not been removed.
In stage I usually nothing else is done (sometimes chemotherapy is given in IBs), but in stage II chemotherapy is usually given later. All these patients should be followed up with control chest CT, not only because of the possibility of tumor recurrence (reappearance of the tumor) but also because of a high risk of new lung tumors in another location.
In stages III there is much controversy. A combined strategy of surgery and radiotherapy with subsequent chemotherapy is generally accepted. Sometimes, in very specific cases, chemotherapy and radiotherapy are given first and then an operation is performed.
The prognosis of stages IV is poor. Radiation therapy is usually administered to reduce the size of the tumor if it is causing local complications, such as compressing neighboring organs, producing hemoptysis (expectation of blood from the respiratory tract), producing recurrent pneumonia, or to treat metastases, remove bone pain , improve brain metastases, etc. In patients with pleural effusion (fluid in the pleura), it is usually removed from time to time and, if it is very recurrent, a pleurodesis can be done, that is, removing the fluid and injecting a substance inside the pleura that prevents the liquid reappears. In patients with previous good performance status, stage IV chemotherapy is sometimes recommended. Associated with chemotherapy, bevacizumab, an antibody directed at VEGF (vascular endothelial growth factor), can be administered. Although it increases survival, it favors bleeding, so it is not indicated in all patients.
The presence of a mutation in the tumor cells modifies the treatment. Erlotinib (Tarceva), gefitinib (Iressa), and afatinib (Giotrif) are inhibitors of a substance (EGFR kinase) that has been identified in a small proportion of patients with non-small cell lung cancer. Crizotinib (Xalkori) is an inhibitor of the ALK oncogene. In patients with these mutations, the response to these treatments is good. This treatment should be offered to all patients with the mutation regardless of the stage of the tumor. Treatment should be continued until the disease is seen to progress despite treatment. These medications can cause skin lesions and diarrhea.
In addition to the previous treatment guidelines, support treatment should be administered with a good diet, treatment with analgesics if there is pain, radiotherapy on specific metastases that can be very painful, etc.