MfA - Lung Cancer

Medicine for Africa - Medical Information Service

UNG ANCER

Definition:

Lung cancer is also called pulmonary carcinoma or bronchogenic carcinoma. It consists of malignant cell growth of either the tissue, lining the bronchopulmonary tracts or of the parenchymal (functional) lung tissue.

Lung cancer is one of the most common cancers throughout the world, and is the leading cause of cancer deaths in both men and women worldwide.

Smoking is clearly THE most frequent cause of lung cancer, causing up to 90% of all cases. Ninety-nine percent (99%) of small cell lung carcinomas (SCLC) develop in smokers, while the so-called non-small cell lung carcinomas (NSCLC) develop in about 70% (bronchioalveolar carcinoma) to 98% (squamous cell carcinoma) of all cases in smokers. Passive or secondary smoking is also associated with an increased risk of cancer development – it is considered causative in up to 25% of all lung cancers which develop in non-smokers.

Other risk factors include the exposure to high levels of pollution, to radon and particularly to asbestos, but also to arsenic, gas fumes and radioactive substances. Occasionally, a tumor can develop in lung scars, caused by previous, now healed lung infections such as tuberculosis. Increased familial occurrence of lung cancer points to the presence of a genetic risk factor.

The non-small cell lung carcinomas are grouped together, because their prognosis and management are similar – their three main subtypes consist of:

Squamous cell carcinoma (SCC);
Adenocarcinoma;
Large cell carcinoma (LCC).

Squamous cell carcinoma is the most frequently occurring form of all lung cancers with more than 31% of cases; it typically arises from the epithelial or lining cells of larger and smaller airways, which is why it is also called bronchogenic carcinoma.

Adenocarcinoma accounts for slightly less than 30% of all lung cancers; it typically develops in the peripheral lung tissue. While adenocarcinoma is clearly associated with smoking, it is also the most frequently occurring type of lung cancer in people who have never smoked. A subtype of adenocarcinoma is the so-called bronchioalveolar carcinoma, which arises in the distal airways and air-blood transferring alveoli. This type of cancer is more common in non-smoking women, and requires a different approach to treatment.

Small cell lung cancers (SCLC) are also called ‘oat cell carcinomas’, because the shape of the cancer cells resembles the shape of oat kernels. While this type of tumor is less common, it grows rapidly in the large airways (bronchi), spreading to smaller airways. The ‘oat’ cells contain dense neurosecretory granules, containing neuroendocrine hormones, which cause the so-called ‘paraneoplastic syndrome’; this is a group of syndromes that may include the ‘Syndrome of inappropriate antidiuretic hormone – SIADH’, the ‘Cushing syndrome’, as well as other neurologic problems.

Symptoms:

Sometimes, lung cancers do not show any symptoms prior to diagnosis – up to 25% of all lung cancers are diagnosis during routine chest x-rays or other routine procedures.

The most frequent symptom – persistent cough – appears in up to 75% of all patients. Weight loss and chest pain can be seen in about 40% of people with lung cancer, and increasing breathing problems appear in about 20% of patients. Bloody cough, bloody expectoration, as well as cough which lasts for more than three months, require immediate check-up by a family practitioner or another medical professional.

Also, repeatedly occurring pulmonary infections, persistent hoarseness, piping breath, shortness of breath, and swelling in the head and neck area, are all symptoms which may point towards the development of a tumor and have to be worked up by a physician.

Diagnosis:

The first step for evaluating the patient’s health status consists of a thorough physical examination, with specific emphasis on the bronchopulmonary system, if the patient’s symptoms point to this system.

The first test will be a simple sputum examination from a deep cough, which the pathologist will examine under the microscope, and a chest x-ray, which will be diagnosed (‘read’) by a radiologist. If the suspicion of a tumor is confirmed, a bronchoscopy will be the next step, when a flexible tube will be inserted into the airways, in order to visually inspect the bronchopulmonary tree and to harvest cells and tissue biopsies from suspect areas.

Additional exams may include a computer tomogram (CT-scan), a special kind of x-rays, or a Magnetic Resonance Imaging (MRI) procedure, which is a special photography by radio waves directed by a magnet. Often, a fine needle aspiration (FNA) biopsy will be performed, if available, in which tissue or fluid from the lung is obtained by inserting a needle under guidance by CT-scan or ultrasonography. The x-ray tests can very precisely localize the tumor and determine its size, as well as the possible existence of satellite tumor nodules (metastases) in other organs, while the FNA can provide a histological (cell) diagnosis as to the kind of malignant cells the tumor exhibits.

The definite diagnosis for a malignant tumor requires a tissue biopsy, obtained either by FNA or open biopsy (which requires a larger incision into the chest wall and artificial respiration), and the subsequent examination of these cells (histology) under the microscope by the pathologist. According to the histology, lung cancers are divided into three different types of tumors; among the most frequent types are:

Small cell lung carcinoma – SCLC;
Non-small cell lung carcinoma – NSCLC, including squamous cell carcinoma, adenocarcinoma, bronchioalveolar carcinoma, large cell carcinoma, and undifferentiated carcinoma;
Carcinoid tumor – a hormone producing tumor.

The lung cancer has to be staged according to its growth and spread within the lung, as well as the presence of satellite cancer cells (metastases) outside the lung parenchyma and/or in other organ systems. While the three above listed carcinoma groups have specific sub-staging systems, the overall staging system for lung cancer uses the so-called TNM system:

‘T’ indicates the size of the primary tumor mass and whether it has grown into nearby areas:

T0 – no evidence of tumor;
TIS – ‘carcinoma in situ’, cancer cells are found only in the top layers of lining cells and do not invade deeper lung tissue;
T1 – tumor size is less than 3 cm in diameter;
T2 – tumor is larger than 3 cm in diameter, and/or invades a main bronchus or the visceral pleura of the lung, and/or blocks partially the airways;
T3 – tumor can be any size, but also:

Grows into the muscles of the chest wall (diaphragm), the membranes between the right and left lung (mediastinal pleura), or the sac that contains the heart (parietal pericardium), and/or
Invades the main bronchus and is located near the bifurcation of the trachea (windpipe), and/or
Has grown into the airways, causing an entire lung to collapse;

T4 – a tumor of any size, which has spread beyond the lung tissue into neighboring tissues and organs, such as the chest bone, the heart, the large blood vessels, the trachea, the esophagus, or the backbone, or consists of two or more separate tumor nodules in the same lobe of the lung, or there is malignant pleural effusion present (tumor cells in the space surrounding the lungs).

‘N’ stands for lymph nodes, and describes the extent of cancer spread to regional lymph nodes:

No – no spread to nearby lymph nodes identified;
N1 – lymph nodes which are located on the same side as the primary tumor contain cancer cells;
N2 – lymph nodes on the same side of the primary tumor are affected which are located near the bifurcation of the trachea (carina), or behind the breastbone or near the heart (mediastinum);
N3 – lymph nodes which are located near the collar bone on either side, and/or lymph nodes on the opposite side of the primary tumor are affected with cancer cells.

‘M’ stands for ‘metastases’, and indicates whether the cancer has spread to other organs of the body, such as brain, liver, or bones):

M0 – no evidence of tumor spread to distant organs or areas;
M1 – the cancer has spread to one or more distant sites, including another lobe of the lung, distant lymph nodes (see above) or other organs.

Once the TNM system has been assigned, the tumor will be grouped into an overall stage, identifying the cancers prognosis and potential ways of treatment. A short summary of the Stages 0, I, II, III and IV (refer to TNM classification above):

Stage 0 – TIS, N0, M0;
Stage IA – T1, N0, M0;
Stage IB – T2, N0, M0;
Stage IIA – T1, N1, M0;
Stage IIB – T2, N1, M0, or T3, N0, M0;
Stage IIIA – T1, N2, M0, or T2, N2, M0, or T3, N1, M0, or T3, N2, M0;
Stage IIIB – any T, N3, M0, or T4, any N, M0;
Stage IV – any T, any N, M1.

The TNM system is primarily used for NSCLC, less so for small cell lung carcinomas, because treatment and prognosis for SCLC do not vary as much as with NSCLC. Also, SCLC is usually already far advanced and has spread well beyond its original site at the time a first diagnosis has been made.

Treatment:

The therapy depends foremost upon the kind of tumor (histology/histopathology) and the extent of the tumor spread (metastases).

Surgery is usually performed in very early stages of a carcinoma, or a locally limited carcinoid tumor. Depending on the size of the tumor, a small area of lung tissue, an entire lobe of lung tissue, or a whole lung will be removed. Surgery is more often used in NSCLC, and can only be effective in small, early-on diagnosed SCLCs, since these tumors often spread widely, even prior to diagnosis.

Radiation therapy often follows the operation, or is given when surgery is not an option. At times, radiation is also given as a preventive measure against the development of metastases (especially in the brain). Recently, laser therapy has also been used.

Chemotherapy follows radiation therapy, or replaces surgery in advanced cases. In chemotherapy, medications are given to kill remaining cancer cells anywhere in the body (tissue, blood) – it is a ‘systemic treatment’, encompassing the entire body system, since the drugs are dispersed throughout the body and into all organs via the blood circulation.

Chemotherapy and/or radiation therapy are the preferred methods of treatment for SCLC.

Side effects of radiation and chemotherapy can include hair loss and changes in blood count, both of which usually return to normal after cessation of the treatment.

New forms of treatment such as laser therapy, photodynamic therapy (special light rays combined with specific chemicals), kryosurgery (freezing of the tumor tissue prior to removal), and the development of specific antibodies against cancer cells, are all still in different stages of research.

Worth mentioning are also angiogenesis inhibitors. Angiogenesis means the development of new blood vessels, which are induced by the tumor to feed it and to help it grow. Scientists are trying to inhibit this development of new vessels selectively, i.e. in the area of the tumor, by so-called angiogenesis inhibitors, in order to starve the tumor. Biotechnology, the identification of the human DNA, and recently developed stem cell research, are new therapeutic methods in research, which may promise completely new ways of treatment for the future.

The prognosis of lung cancer depends for one on the type of cancer and its size, and secondly, on how well the tumor responded to the treatment. The overall 5-year survival rate of lung cancer is around 15%. However, every patient and every tumor is different and cannot necessarily be compared with each other. However, one’s personal attitude towards the disease and the will to live and to fight the cancer, DO have an undisputed influence on the outcome, even if this influence cannot be measured statistically.

Talk to your doctor – he knows your specific case, and is the only person who can give you an appropriate judgment.

Prevention:

The best prevention is – QUIT SMOKING – or, even better, never start smoking!

Avoiding exposure to the above mentioned substances and chemicals is very important, or, at least, taking appropriate precautions, while being exposed to them.

Non-smokers are helped by the increased number of places and buildings where smoking is now prohibited.

A balanced diet, in order to strengthen one’s immune system, and a healthy lifestyle with sufficient bodily activities, are good general preventive measures against different kinds of diseases. These measurements can also be helpful against certain types of tumors.

Vitamins, especially vitamin A, are said to have a protective effect against lung cancer.

Anti-smoking plasters have been around for years, recently joined by anti-smoking pills, all of which are supposed to wean you away from cigarettes. Accompanying psychological treatment can often increase the success rate.

There are also self-help groups, similar to ‘Alcoholics Anonymous’, where people receive help in strengthening their will to quit smoking through group therapy. All these methods show varying success rates, which, however, are primarily influenced by the WILL of each and everyone to REALLY stop smoking.

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DISCLAIMER: The above article is only intended to provide general information regarding this topic. It is not intended and does NOT replace the need to consult a medical or other professional person, if you have or believe to have this disease/disorder. While the article was researched, written and reviewed by medical professionals, and Medicine for Africa, its staff and publisher made every effort to assure accuracy and correctness, it does not claim to be complete, correct or to reflect the very latest stand of medical/scientific knowledge in the disease’s/syndrome’s pathology, diagnostic and/or therapeutic development. Medicine for Africa, its founder, management, staff, writers, reviewers or publishers may NOT be made responsible or legally bound to any information provided above, and cannot be held liable to any conclusions or decisions the reader may draw after reading this article. The reader is explicitly advised to consult a licensed physician and to present his/her specific situation before making any health related decisions.