Support Us: [email protected]
What is meant by cancer?
Each organ in the human body is made up of millions of tiny cells. These cells only survive for a short period. They then die and are replaced by new cells. This process of cell death and growth happens daily. It is usually very tightly controlled to stop excessive cell growth. When cells in an organ "escape" this normal control mechanism, they can multiply drastically to form a cancerous growth called a tumour. When this growth takes place in the lung, we call it lung cancer. In most cases of cancer in the body, we do not know what sets off this abnormal cell growth. However, in the case of lung cancer, cigarettes or tobacco smoking is the commonest culprit.
Who gets lung cancer?
Cigarette smoking is the No. 1 risk factor for lung cancer. Cigarettes contains hundreds of harmful substances called carcinogens, i.e. they are known to cause cancer. It does seem that the longer you smoke, and the more cigarettes per day you smoke, the more likely you are to develop cancer. Lung cancer can also be caused by exposure to someone else's smoke, also known as passive smoking. Rarely, lung cancer can develop in someone who has only smoked for a short time, or never smoked at all. This is unusual. Lung cancer can be caused by heavy exposure to other harmful inhaled substances, such as radon and asbestos dust. The major cause is cigarette smoke, however. People most commonly present with lung cancer in their 60's. However, it does occur in younger and older age groups.
Lung cancer claims more lives yearly than breast cancer, colon cancer, and prostate cancer combined. WHO data says lung cancer killed approximately 1.7 million people worldwide in 2015 making it the most lethal of all cancers.
Lung cancer will soon overtake breast cancer as the most common cause of cancer in women. It is already the most common cause of cancer in men. This makes the high rates of smoking among young women more worrying.
Symptoms of lung cancer
One of the major problems with lung cancer is that, by the time it starts to cause symptoms, it is usually quite advanced. In the early stages of the illness, there are usually no symptoms. The first symptom is usually development of a cough, or worsening of a pre-existing cough. The patient may notice streaks of blood in the phlegm. Shortness of breath, weight loss and fatigue are usually seen in the later stages of the illness. Pain is unusual in lung cancer. This is unless the cancer invades bone, such as the ribs or spine. Headache or confusion may be seen if the cancer has invaded the brain. Sometimes, the cancer is seen on a chest x-ray or CT Thorax done for other reasons, with the person having no or unrelated chest symptoms. In this instance, the cancer may be picked up at an early stage.
How do doctors diagnose lung cancer?
Lung cancer usually is first suspected after an abnormal shadow on a chest x-ray (CXR) is noted. A CT scan of the lungs or CT Thorax is then done to give a more detailed image of this shadow. These days it is common to do a CT Thorax with selected views of the abdomen to see if the tumour has spread beyond the lungs to abdominal organs like the liver or the adrenal glands. A detailed history, examination and bloods will influence the need for other imaging including dedicated spinal imaging or brain imaging. An integrated positron emission tomography with a full body CT (PET-CT) is currently done during the initial diagnostic phase both for diagnosis and staging if there is suspicion from the original CT of tumour which has potentially spread outside the lungs. Patients are given contrast called fluorodeoxyglucose (FDG) which is taken up by tumour cells indicating the tumour’s metabolic activity. The standardised uptake value (SUV) has been shown to correlate well with prognosis of the lung cancer.
The main step in diagnosis involves a biopsy of the shadow suspected to be lung cancer. This is the definitive test to obtain tissue to confirm lung cancer. This can be achieved either via the airways using bronchoscopy or through the skin guided by a simultaneous CT Thorax. Frequently a specialised type of bronchoscopy is done called a EBUS-TBNA where a bronchoscope with an endobronchial ultrasound (EBUS) on the tip is used to aspirate lymph node contents from within the chest cavity (TBNA-transbronchial needle aspiration). Occasionally the first biopsy is taken from a suspicious area outside the chest e.g. the liver to help both diagnose and stage the cancer simultaneously.
Types of lung cancer
Broadly speaking, there are 2 types of lung cancer. These are called non-small cell cancer and small cell cancer, based on their appearance under the microscope. Non-small cell cancer is much more common. It tends to grow more slowly. Surgery or radiotherapy is the usual treatment for this. Small cell cancer is less common and grows more quickly. It has almost always spread beyond the lung at the time of diagnosis. Surgery is usually not an option. It is usually treated with chemotherapy (see below).
Treatment of lung cancer
Treatment for lung cancer follows the general principles for cancer treatment which is to first consider the type of lung cancer, staging or extent of the spread of the cancer and the physical functional status of the patient. Curative therapy should always be considered if possible. Curative treatment mainly surgery should only be attempted if all grossly detectable disease can be removed and the likelihood of death from occult metastatic disease is reduced. If curative resection is impossible, chemotherapy and/or radiotherapy is the next option. Stereotactic body radiotherapy (SBRT) is an alternative non-surgical radiation technique which is emerging as effective treatment for localized lung cancer in non-surgical candidates.
Radiotherapy can also be very useful for controlling pain due to spread of the cancer to the bones. It can also be delivered to the head if the cancer has spread to the brain. Each course of radiotherapy is called a cycle. Usually several cycles are given over the course of a few days or weeks. The response to radiotherapy is not immediate. It usually takes a few weeks to work. Side effects from radiotherapy are few. You may feel a little tired after treatment. You may also notice a slight discomfort on the skin like sunburn.
Chemotherapy is a form of treatment that is very effective for some types of lung cancer, especially small cell cancer. This involves giving medication which makes cancer in the body shrink or disappear. The medication is usually given in the hospital. It is in the form of injections through a "drip". Sometimes, chemotherapy can be given in tablet form. Nowadays, chemotherapy has fewer side effects which will all be explained to you by your doctor in detail (oncologist or cancer specialist). Sometimes, the different treatments will be combined, if the doctor feels that it is appropriate. In some cases, no immediate treatment is given. This is especially if the cancer is small or slow-growing. A "wait-and see" approach is taken, which means observing the cancer's growth over time.
Future Directions in lung cancer treatment
The discovery of driver mutations has opened a new range of targeted therapies for lung cancer beyond conventional cytotoxic chemotherapy. Unlike chemotherapy which is unselected in killing both cancer cells and normal cells, targeted therapies rely on the inhibition of selected driver mutations behind uncontrolled tumour proliferation. A patient whose lung cancer has the epidermal growth factor receptor (EGFR) mutation can be treated with a tyrosine kinase inhibitor like erlotinib with good results. If a patient with advanced non-small cell lung cancer is identified to have the Alk translocation mutation, a medication like crizotinib has shown promising efficacy in recent trials.
The future will also see more sensitive and non-invasive means of detecting these lung cancer mutations. There are now blood tests which allow screening for specific lung cancer mutations using peripheral blood rather than the traditional tissue biopsy. The term “liquid biopsies” has been coined to describe this diagnostic technique. There is evidence that tumour cells are shed into the circulating blood stream or circulating cell-free tumour DNA which can be sampled and checked for driver mutations. Currently there is 2 “liquid biopsies” readily available for EGFR mutation screening. It is important that all patients be screened for driver mutations and recruited into appropriate cancer trials to allow them to receive the best treatment.
The outcome of lung cancer treatment varies widely. Some people do extremely well, and others not so well. A positive outlook can go a long way. People with advanced disease can sometimes do very well. Every case is taken on its merits. Doctors do not like to predict how a person will respond to treatment. This is because everyone responds differently. Even if there is no cure for a person's cancer, modern drugs are very effective at controlling cancer symptoms like breathlessness and pain. This means that no-one with lung cancer, should suffer thanks to good palliative medicine.