Lung cancer
Contents:
General
The lungs are located behind the rib cage and are made of spongy, elastic tissue that stretches and constricts with breathing. The lungs and airways (trachea and bronchi) bring in fresh, oxygen-enriched air and get rid of waste carbon dioxide. They also help to regulate the concentration of hydrogen ion (pH) in the blood.
Lung cancer is caused by the uncontrolled growth of abnormal cells in one or both of the bronchi, or on occasion the lungs themselves. Normal lung tissue cells reproduce and develop into healthy lung tissue; abnormal cells reproduce rapidly and form tumours. The tumours, then disrupt the lung, making it difficult to function properly.
Lung cancer if left untreated can spread to lymph nodes or other tissues in the chest. It can also metastasize (or spread) throughout the body, to the bones, brain, liver, or other organs.
Around 90% of lung cancers are smoking related, because of this link there can be a social stigma attached to lung cancer. A study in America showed that 78 % of doctors feel that society perceives lung cancer to be a self-inflicted disease, and that if we could remove this stigma patients would be more encouraged see their doctor.
Types of lung cancer
There are two main types of lung cancer, non-small cell (80% of all cases) and small cell (20% of all cases).
The names refer to the kinds of cells that make up the tumour, not the size of the tumour.
Non-small Cell Lung Cancer
Non-small cell lung cancer is classified into three subtypes:
Aden O carcinomas - found in the mucus glands (the glands that make mucus to line the airways and lungs to catch dirt and germs and keep the lungs clean)
Squamous or epidermoid carcinoma - located in the bronchial tubes (the airways that lead to the lungs)
Large cell carcinoma - found usually in the substance of the lung
Small Cell Lung Cancer
Small cell lung cancer is more heavily associated with smoking. The tumours grow and spread quickly. There are two stages of the disease: limited and extensive, according to whether it is confined to the chest or spread outside.
Risk Factors
Tobacco
Smoking cigarettes, pipes or cigars greatly increases the risk of lung cancer. Around 90% of lung cancers are smoking related. However, not all smokers develop lung cancer. Quitting smoking significantly reduces an individual's risk, although former smokers remain at greater risk for lung cancer than people who never smoked.
Environmental tobacco smoke (passive smoking)
Spending time in smoky environments such as bars and restaurants can increase your risk of lung cancer. Many European countries are restricting smoking in public places to limit the risks of passive smoking and protect workers.
Industrial carcinogens
Exposure to industrial carcinogens, including asbestos, arsenic, nickel, chromium, zinc, polycyclic hydrocarbons and radon gas can increase the risk of lung cancer, especially when combined with cigarette or cigar smoking. It is thought that up to 15% of lung cancer cases in men (5% in woman) may be caused by occupational factors and smoking.
Exposure to radiation
Exposure to radiation from occupational, medical and environmental sources can increase the risk of lung cancer.
Air pollution
Outdoor air pollution may also increase the risk of lung cancer. It is thought approximately 1-2% of lung cancer cases are from outdoor pollution.
Diesel exhaust fumes
Heavy occupational exposure to diesel exhaust may increase the risk of lung cancer.
Tuberculosis (TB) or Pneumonia
Having had a previous lung disease such as tuberculosis or pneumonia has been related to a very slight increased risk.
Beta-carotene supplements
Beta-carotene supplementation may increase lung cancer mortality in smokers.
Family inheritance/Genetics
Some studies indicate that an inherited gene or genes as well as tobacco smoke increase the risk of lung cancer although to date no major genes for lung cancer have been identified. The fact that only 10-20% of smokers develop lung cancer implies that inherited factors influence the effects of tobacco. There is lots of interest in variants of genes that help detoxify the carcinogens in tobacco smoke such as P450, GST and XPD.
Prevention
Stop smoking
Stopping smoking immediately lowers the risk of contracting lung cancer. The risk for former smokers remains higher than non-smokers, however the risk continues to drop for every year without tobacco smoke. After 10 years of abstinence, a person who has quit smoking reduces their risk anywhere from 30 to 50 %.
Avoid Smoky areas
Limit time spent in smoky areas.
Limit exposure to radiation and chemicals
Ensure precautions are taken at work and home to limit any exposure to harmful radiation and chemicals.
Vaccinate against TB
There is a vaccination available that can significantly reduce the risk of contracting TB.
Healthy eating
Intake of fruit and to a lesser extent vegetables may have a slight protective effect.
Screening
Currently there is no European screening test for lung cancer that has proven to increase survival rates.
Early detection of lung cancer is critical to improving survival. Testing people that are known to be at high risk for developing lung cancer can help to find tumours that are small and more easily treated. Those at high risk include men and women:
60 years of age who currently smoke or have a history of smoking
- with previous lung tumours
- With chronic obstructive pulmonary disease (COPD)
Low-radiation dose spiral computed tomography
Researchers are always looking for new ways of detecting lung cancer at an early stage. The most promising recent technology is the low-radiation dose spiral computed tomography (CT) scan. Recent trials done in Japan and the United States have documented that low-dose CT can diagnose lung cancer at an early stage in high-risk individuals.
Reports of Japanese trials of almost 10,000 scans showed a detection rate significantly better than chest x-ray, a higher rate of Stage I lung cancers, and an increased survival at three years.
Low-dose CT could be come a widespread screening tool. It requires less than 20 seconds of scanning time with minimal radiation exposure and it costs only slightly more than a chest x-ray. The promising results of the Japanese studies have become the basis for broader trials using low-dose CT scan. These studies will help to decide if low-dose CT scanning should become part of national screening programmes .
Spiral CT Scan
A newer and more controversial diagnostic tool for detecting lung cancer is the spiral, or helical, CT scan. The spiral CT scan can image the lungs in a single breath hold. Although spiral CT scans can detect tumours in the earliest stages of disease, there is a debate about whether this earlier detection saves lives. Some experts are concerned that screening will lead to over diagnosis, or the detection of cancers that would not have caused symptoms prior to patients dying of other causes.
False positives also are common with baseline CT scans (the first time a person has one) because the test can mistake scar tissues from an old infection, or a benign lump, for cancer. In addition to the mental anguish resulting from a false positive, patients may undergo a needle biopsy, which may result in the collapse of the lung. Many medical professionals feel this risk can be managed by monitoring the growth rather than immediately performing a biopsy.
The newer imaging scans are very sensitive and can reveal cancerous growths not seen by conventional chest X-rays. Clinical trials are underway to determine the effectiveness of this screening.
Symptoms
The symptoms of lung cancer may take years to appear and are often confused with less serious conditions. Signs and symptoms may not appear until the disease reaches an advanced stage.
Chest symptoms
- Smoker's cough that persists or becomes intense
- Non-smoker's cough that lasts for more than two weeks
- Persistent chest, shoulder or back pain unrelated to pain from coughing
- Change in colour of sputum (saliva, phlegm, or mucus coughed up from the respiratory tract)
- Increase in volume of sputum
- Blood in sputum
- Wheezing
- Recurrent pneumonia or bronchitis
Other symptoms of lung cancer may not be chest related
- Fatigue
- Loss of appetite
- Headache, bone pain or aching joints
- Bone fractures not related to accidental injury
- Neurological symptoms such as loss of memory or loss of balance
- Neck and facial swelling
- Unexplained weight loss
There may also be signs and symptoms caused by the spread of lung cancer to other parts of the body. Depending on which organs are affected, these can include headaches, general weakness, pain, bone fractures, bleeding, or blood clots.
Diagnosis
Early detection of lung cancer is vital to improving chances of survival. Doctors use a number of tests to detect and diagnose lung cancer which can then determine the type and stage of the cancer and the best way to treat it.
Tests Include:
Physical Examination
Physical examination is important for detecting any signs of cancer such as swollen lymph nodes in the neck or collarbone area and also for checking overall health.
Chest examination
Examining the chest and listening to the lungs with a stethoscope can help detect abnormal breathing sounds or patterns.
Chest X-ray
X-rays are 'flat' pictures of the lungs, which can show up abnormal growths.
CT or CAT scan
Computed tomography (CT) also known as a CAT scan is a sophisticated instrument that can create a two-dimensional scan from a series of X-ray images. CT scans reveal much more detail than x-rays. The newest version of the CT is called a helical (or spiral) scan and is even more sensitive than regular CT scans.
MRI scan
Magnetic Resonance Imaging (MRI) is similar to a CT scan except it uses a magnetic field in place of X-rays to create an image.
PET scan
Positron Emission Tomography (PET) is a scan that traces the way the body cells use sugars and other chemicals for survival. PET scans can find cancerous tumours because the tumour takes up radioactive sugar making them easier to see.
Sputum cytology
Coughed-up phlegm from the lungs is examined under a microscope to check for abnormal or cancerous cells.
Bronchoscopy
A specialist can view the lungs through a hollow, flexible tube (bronchoscope) that is passed through the nose and throat into the main airway of the lungs. If abnormal areas or tumours are seen biopsies can be obtained through the bronchoscope.
Biopsy
If lung cancer is suspected, a biopsy or sample of lung tissue is taken for examination under a microscope. Biopsies are obtained in different ways depending on the location of the tumour:
- through a bronchoscopy
- by inserting a needle through the chest into the lung
- by removal and examination of an enlarged lymph node in the neck
- by a small operation on the lung
Treatment
After a patient is told they have lung cancer the most appropriate treatment will be discussed. The course of treatment depends not only on the type and stage of lung cancer , but also the general health of the patient. The principal forms of therapy for lung cancer are surgery, radiation , and chemotherapy . This may be used in different order (sequence) according to the individuals patients cancer.
Surgery
Surgery can offer the greatest chance of survival for many types of lung cancer , only if the cancer has not yet spread (or metastasized ) to other parts of the body. Surgery can also treat complications seen in advanced disease. Most patients will undergo some type of surgery throughout the course of their diagnosis and treatment.
Three general types of surgery include:
Curative surgery : The removal of a tumour when it appears to be confined to one area. This type of surgery aims to completely remove the cancerous tumour, and may include removing a wedge, lobe, or an entire lung.
Debulking surgery : Type of surgery performed when the entire tumour cannot be removed. The remaining portion of the tumour is then treated with chemotherapy and/or radiation .
Palliative surgery : Used to shrink a tumour that is causing discomfort or disability.
Chemotherapy
Chemotherapy uses strong chemicals or drugs to prevent the reproduction of cancer cells and stop their growth. Chemotherapy can be used along with radiotherapy and surgery. These drugs are often given before or after surgery and in different combinations to more effectively target the cancer, depending on the size and location of the tumour.
Drug combinations for lung cancer have usually included cisplatin and a vinca alkaloid and more recently a taxane.
Chemotherapy drugs may be given through a drip or taken orally in tablet, capsule, or liquid form. Chemotherapy drugs circulate through the entire body via the blood stream and can kill cancer cells missed by surgery or radiotherapy.
The amount of chemotherapy a patient receives depends on the type of cancer, the drugs, and the patient's overall response to treatment. Therapy may be given daily, weekly, or monthly, and can continue for months or even years. Some drugs may be given in cycles, with rest periods in between treatments, to allow the body to recover and produce new, healthy cells.
Side effects of chemotherapy
Side effects vary depending on the type of chemotherapy and how the patient responds.
Chemotherapy side effects may be extremely uncomfortable, but most symptoms are temporary and gradually disappear after the treatment ends. There are medicines available to help manage many of the side effects.
Nausea and Vomiting
Chemotherapy may cause nausea and vomiting. However eating is very important to provide strength to help the patient feel better. To lessen symptoms patients should eat and drink slowly and avoid eating fried or fatty foods.
Hair Loss
Hair loss can occur on all parts of the body. Sometimes hair falls out completely, while other times the hair grows thinner. In most cases, hair grows back after the treatment is completed, but may be a different texture or thickness.
Fatigue
Chemotherapy affects the bone marrow and the body's ability to produce red blood cells , which may temporarily cause anemia . Anemia often makes patients feel weak and tired.
Infections
The effect of chemotherapy on bone marrow may also lower the amount of white blood cells, which help fight infection. To prevent infection, patients should avoid exposure to people who have a cold, flu, or any other contagious diseases.
Bleeding
Chemotherapy can affect other blood cells called platelets, which may lead to easier bruising or bleeding.
Radiation/Radiotherapy
Radiation therapy involves the use of high-energy X-rays to kill cancer cells or prevent them from growing.
Radiation oncologists or radio therapists use equipment to target the X-rays directly at the tumours . The treatment aims to destroy the cancer cells with minimal radiation exposure to healthy cells.
Radiation therapy is often spaced over a number of weeks or months so that the healthy cells that may be affected have time to rejuvenate.
The number of treatments a patient receives depends on the type and extent of the tumour, as well as the radiation dosage and how the patient's tolerance is affected by the treatment.
Side effects of radiation therapy
Depending on the treatment side effects may vary. Some may be severe, but often disappear once the therapy is completed.
Fatigue
Fatigue is the most common side effect associated with radiation therapy. A patient undergoing radiation should rest at night and relax as much as possible during the day.
Sickness/Nausea
Nausea may occur with radiation therapy however it is important to eat so that the body has enough nutrients to repair damaged cells. Patients should try to eat lots of small meals throughout the day. Medicine can be prescribed to prevent nausea.
Hair Loss
Loss of hair may occur in the area of the body being treated, only the hair in the direct path of the radiation will be affected.
Skin Reaction
The skin in the treatment area may become dry, irritated, and sensitive, and should be treated gently. The affected area should be kept out of direct sunlight for at least one year after treatment.
Gene Therapy
Gene therapy is a new approach that interferes with the growth of tumour cells. When lung cancer progresses suppressor genes sometimes called 'guardian genes' (P53 genes) are destroyed. P53 mutations are present in 80 percent of lung cancers. Research in laboratories has shown that P53 gene replacement therapy causes the tumour to shrink, especially when combined with cisplatin. How the gene therapy is delivered remains a major obstacle to widespread use of this approach and requires more research.
New gene therapy treatments being researched
Getitinib (Iressa) can be used to treat advanced cases of non-small cell lung cancer. Getitinib inhibits tumour cell growth by interfering with the EGFR enzyme tyrosine kinase. Early studies demonstrated that a few patients with lung cancer who had received previous treatments had a decrease in the size of their tumours when given Getitinib alone and in combination with other chemotherapy drugs.
Cetuximab is another EGFR blockage agent being researched. Cetuximab is a monoclonal antibody that competes with EGF for binding to its receptor. It has shown anti-tumour effect when used alone and in combination with chemotherapy and radiation. Further clinical trials are in progress.
Statistics
- Lung cancer is the most common cancer in the world with 1.2 million new cases diagnosed every year.
- Lung cancer is the most frequently occurring cancer in Europe , the most common type of lung cancer is squamous cell carcinoma.
- In Britain one person every 15 minutes is diagnosed with lung cancer.
- Lung cancer is the most common cause of death in the UK around 33,600 deaths each year, and overtook breast cancer deaths in women some years ago.
- Lung cancer is rarely diagnosed in people under 40 years old
- Male to female ratio is 3:2 (23,000 male cases and 15,000 female cases in 2000, UK )
- Globally the highest rates in lung cancer in men are found in Eastern Europe and North America.
- Hungary and Poland have the highest standardised rates for male lung cancer in the world
- Globally the highest rates in lung cancer in women are found in North America and Europe.
- Denmark , Hungary , Iceland and UK have some of the highest standardised rates for female lung cancer in the world
- Africa and Asia have the lowest rates of lung cancer in men and women
Ethnicity
- In the UK South Asians have a lower rate of lung cancer than non South Asians
- In America lung cancer rates are higher in the black population for both male and females compared to whites
- In America Hispanics and Asians have lower rates than whites
Deprivation
- Lung cancer incidence and mortality rates are strongly associated with deprivation. 1993 data in the UK showed that incidence of lung cancer was 2.5 times higher in the most deprived male groups compared to least deprived – incidence in women was even higher at 3 times.
Survival
- Lung cancer has one of the lowest survival outcomes of any cancer. In England and Wales around 25% of patients are alive one year after diagnosis and this falls to 7% at 5 years.
- Five year relative survival estimates for the US are 13% for men and 17% for woman
- The highest five year survival rates in Europe are in Austria ,France , Germany , The Netherlands and Spain at around 11-13% for men and 11-16% for women.
Mortality
- Lung cancer accounts for 6% of all deaths in the UK and 22% of all cancer deaths
- European rates vary considerably and countries are at different stages in their lung cancer epidemic because of different histories of tobacco smoking and the long latent period between smoking and lung cancer development
Smoking
- World-wide approximately 1.3 billion people currently smoke cigarettes or other tobacco products
- By 2030 it is estimated that 10 million people will die annually from smoking related diseases, 70% of these deaths in developing countries
- In Europe there is a wide variation in smoking prevalence. Of concern is the fact that in every country (except Denmark ) young people are more likely to smoke that older people
- In Spain fewer than 5% of Spanish women aged 45-74 smoke compared to nearly 40% of young women (aged 30-44)
- In 2002 27% of men in the UK (aged 16 and over) were reported as smokers
- In 2002 25% of women in the UK aged 16 and over were reported as smokers
- In 2002 31% of adults in the UK in manual occupations smoked as opposed to 20% in non manual jobs
Passive Smoking
- 2002 IARC report concluded that the risk of lung cancer for non smokers was increased by 20-30% if they lived with a smoker and by 16-19% if they were exposed in the workplace.
- ASH (action on Smoking and Health) has estimated that around 600 lung cancer deaths each year in the UK are caused by passive smoking.
Stopping smoking
- If people who have been smoking for many years stop, even well in to middle age, they avoid most of the their subsequent risk of lung cancer
- Stopping smoking before middle age avoids more than 90% of the risk attributable to lung cancer
- Duration of smoking has more effect than the amount smoked. Smoking one packet of cigarettes a day for 40 years is around 8 times more hazardous than smoking 2 packets a day for 20 years.
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