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Lung cancer is one of the most common cancers and despite treatment advances the cure rate is still very low.
Cancer is no longer the bogeyman it once was, thanks to huge advances in diagnosis and treatment.
But with certain types of cancer, we seem to be getting almost nowhere. Take lung cancer for example. It's the third most common cancer in men and the fourth most common cancer in women. Each year, 8,000 new cases are diagnosed.
Yet despite advances in treatment, cure rates remain very low (in the order of about 15 per cent of all cases) and most people are only diagnosed with lung cancer when they have advanced disease, which severely limits the chances of a cure. More than 7,000 Australians die of lung cancer each year.
Our very existence depends on oxygen in the atmosphere, which we get by breathing air into and out of the lungs. Most people breathe without thinking about how this process works. But when it comes to lung cancer, it helps to know what happens when we draw a breath, as any of the structures involved in breathing can be affected by lung cancer.
The lungs themselves are two cone-shaped spongy bags that can be inflated with air when we breathe in, and collapse when we breathe out (though not fully).
Each lung is made up of sections called lobes; the left lung has two lobes and the right has three. The lungs rest on the diaphragm a wide, thin muscle that sits below the chest cavity and above abdomen, separating the two. During the breathing cycle, the diaphragm contracts and relaxes, helping to fill and empty the lungs.
When we breath, we 'suck' air in through the nose or mouth, down into the trachea (windpipe) and into the into smaller branching windpipes of the lungs (the right and left bronchi) which branch in turn into smaller pipes (secondary bronchi and bronchioles). The bronchioles terminate in tiny air sacs called alveoli. These are covered in a thin membrane, containing networks of capillaries. Blood flows between the thin walls of the air sacs, allowing oxygen to move from the air into the blood, and carbon dioxide (a waste product from the body) to move back the other way.
There are some important structures in and around the lungs, which can be damaged by cancers growing or impinging on them. They are:
Cancer is a term for a lump or growth caused by cells rapidly dividing, and invading other tissues and sometimes spreading to distant parts of the body. Any type of cell found in the various tissues in the lung can become cancerous. But when it comes to classification, lung cancers are divided into two main types based on how the cancer cells look under a microscope.
Small cell lung cancer accounts for about 15 20 per cent of all lung cancers. Small cell lung cancer has usually spread to other parts of the body by the time it is diagnosed, but it responds well to chemotherapy and radiotherapy.
Non-small cell lung cancer is the term used to describe a range of other types including squamous cell carcinoma, adenocarcinoma, large cell carcinoma and bronchiolo-alveolar cell carcinoma. Non-small cell cancers affect the cells that line the main bronchi and smaller airways and these cancers account for about 80 per cent of all lung cancers. They generally spreads to distant organs at a slower rate than small cell lung cancers, but may spread locally into the chest wall and lymph nodes.
Mesothelioma is a rare, but often deadly, cancer of the cells of the pleural membrane around the lungs. It's almost always associated with previous asbestos exposure, which may have occurred more than 50 years earlier (see our fact file on asbestosis.)
Secondary cancers originate from other areas of the body, but spread to the lungs, forming secondaries (metastases) in the lung. With secondaries there are often multiple cancers, whereas a primary cancer is almost always a single cancer.
As almost everyone knows, cigarette smoking is the major cause of lung cancer being implicated in about 90 per cent of cases.
The more a person smokes, and the longer they smoke (i.e. the younger they start smoking), the greater the risk. There is an average lag period of 20 years between exposure to smoke and the development of lung cancer, which is why it is an uncommon diagnosis in people under 40. Lung cancer is more common in people over the age of 50.
Men are more likely to get lung cancer than women, which simply reflects the fact that historically, men have smoked more than women. However, lung cancer rates in women are rising because of higher rates of smoking amongst women over the past few decades. In addition, there is also an increase in lung cancer in non-smoking Asian women. The cause for this increase is unclear but may include both genetic and environmental factors.
Smoke in the environment (passive cigarette smoke inhaled by non-smokers) is another cause of lung cancer. Inhaling carcinogens in a workplace (such as in the metals processing industries) over long periods of time, is another cause; so is repeated exposure of the lungs to radiation.
Lung cancer symptoms are often very slow to appear and by the time they do appear the cancer is often very advanced. The symptoms may be vague at first, gradually worsening over weeks or months.
Cough lung cancer often irritates the airway linings, provoking the cough reflex. Because the cancer doesn't go away, the cough becomes chronic.
Blood stained phlegm or sputum The cancer may bleed into airways and be coughed up (technically known as 'haemoptysis').
Shortness of breath Breathing may become laboured and difficult, especially after exercise or exertion, as the cancer destroys more and more normal lung tissue.
Hoarse voice The voice may become hoarse due to damage to nearby nerves supplying the voice box.
Recurrent chest infections Simple chest infections become more frequent and take longer to clear up (and/or turn into pneumonia).
General symptoms As it grows, a lung cancer absorbs more and more of the body's energy and nutrients, causing general symptoms, such as weight loss, fatigue and tiredness.
Symptoms from secondary cancers If the cancer has spread to other organs there may be symptoms, such as headaches and bone pain, suggesting the development of other cancers.
Sometimes lung cancer is discovered by chance, such as when someone is having a chest x-ray for another reason (prior to elective surgery for example).
But it's more common for a lung cancer diagnosis to come after a visit to a GP for one or more symptoms listed above. If a GP suspects lung cancer, they will order tests such as an x-ray, a CT scan of the chest, and perhaps an examination of the sputum (spittle and mucus) for cancer cells.
However, to confirm a suspected lung cancer diagnosis, a bronchoscopy is necessary. This involves a chest specialist passing a thin flexible tube with a light and a video camera on the end (a bronchoscope) through the mouth, throat, windpipe and into the larger bronchi of the lungs to look for lung cancer and to take a biopsy if one is present to determine what type of cancer it is. For lesions that are more peripheral and beyond the reach of bronchoscopy a needle biopsy through the chest wall may be necessary.
Other tests such as full body CT or PET scan, and other blood tests are done to see whether the cancer has spread and if so, where.
Unfortunately, because lung cancer often takes so long to be diagnosed, treatment options are more limited and not as successful as in many other cancers.
The type of treatment doctors offer someone with lung cancer, indeed whether treatment can be offered at all, depends on:
Using these indicators, cancers are given a staging from 1 to 4 (with stage 4 being the most aggressive). Staging helps specialists to determine the best type of treatment and its likelihood of success.
The three main treatment options are surgery, chemotherapy and radiotherapy. These are best managed by a specialist oncology team in a cancer treatment centre of a major metropolitan hospital. The aim is to obtain a cure if possible, and if it's not, then to prolong quality of life for as long as possible.
Surgery This involves surgically removing the tumour and some lung tissue around it. Removal of an entire lobe of the lung is called a lobectomy. Removing part of a lobe is called a wedge resection. A pneumonectomy is surgical removal of an entire lung. Surgeons operate by cutting through the chest wall (thoracotomy) or the breast bone (sternotomy). A newer surgical technique, called video-assisted thoracic surgery involves using a video camera to help operate within the chest cavity. It requires much smaller surgical incisions than the traditional techniques, and is gaining popularity in the US.
Surgery is sometimes used for non-small cell lung cancers, but less so for small cell cancers, which are usually treated with a combination of chemotherapy and radiotherapy.
Chemotherapy. This involves the administering of a course of anti-cancer drugs that destroy cancer cells or inhibit their growth, these drugs are usually administered through a drip but are sometimes given as tablets. Chemotherapy is given in cycles, each cycle lasting about three weeks, during which there is three to five days of treatment.
It aims to destroy the cancer cells while doing the least possible damage to the body's other cells.
Radiotherapy. This is a course of high energy rays, such as X-rays, given to kill or shrink the cancer. Radiotherapy is most commonly administered from a source outside the body (external radiation) but sometimes from radioactive materials surgically implanted in the tumour itself.
Laser treatment (Photodynamic therapy). This is a newer, less commonly used treatment used to destroy tumor tissue and prevent complications. It's not used as a cure, but to improve symptoms and quality of life.
As is the case with treatment, the outcome for someone with lung cancer varies according to the type of cancer, how rapidly it's growing, whether it's spread and if so where, and the person's general health.
Cancers that are diagnosed and treated early stand the best chance non-small cell cancers that haven't spread and are treated with a combination of surgery, radiotherapy and chemotherapy have a reasonable prognosis (five-year survival rate of between 50-80 per cent). But if this type of cancer has spread outside the chest, the five year survival rate is less than 15 per cent.
Small cell lung cancer also has a poor prognosis. If confined to the chest, the five-year survival is about 25 per cent. Unfortunately though, most small cell lung cancers have spread by the time they are diagnosed, so cure rates are very low.
Overall, taking all types and stages of lung cancer into consideration, the overall five-year survival rate for all lung cancers is only about 15 per cent.
Unlike some cancers childhood cancers for example progress in treating lung cancer has been very slow. Despite more people being offered chemotherapy and radiotherapy, average survival after treatment has only improved by a few weeks over the last decade.
The fact that it's a largely preventable disease, with much better outcomes if identified early, has led to calls for screening programs to detect cancer in at-risk individuals (ie cigarette smokers). Unfortunately there's no good proof that screening methods (sputum testing, x-rays, CT scans) make any difference to the overall survival rates. So the main weapon against this disease remains prevention. And that means giving up smoking, or better still, not starting in the first place.
Fortunately, smoking rates in Australia have fallen to below 20 per cent and are falling, though very slowly. But that still leaves slightly less than 20 per cent of the population who do smoke. And because the time between exposure to cigarette smoke and the development of lung cancer is so long (about 20 years on average), there are many future cases still in the pipeline; ie current and former smokers who will get the disease. So lung cancer will be with us for many years to come.