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Sunday, March 4, 2012

Lung Cancer

Life Extension
By DR. GARY S. SY

MANILA, Philippines — Lung cancer causes non-specific symptoms, and for this reasons it is generally not diagnosed until a very advanced stage. Only approximately 10 % of patients are operable at the time of diagnosis; most of the remainder will succumb to the illness within six to nine months.

Most lung cancer originates in the cells of the lungs; however, cancer may also spread (metastasize) to the lungs from other parts of the body. There are many different types of growth or tumor that can occur in the lungs. It is conventional to divide growths into benign and malignant, and primary and secondary. A benign tumor is one that is unlikely to spread to become life threatening, whereas a malignant tumor grows rapidly, and spreads, thereby threatening life. This happens by direct invasion of surrounding structures or by spreading through the blood or lymphatic system.

A primary tumor of the lungs is one that has arisen first within the lung tissue; a secondary tumor is one that has arisen elsewhere in the body, but has then spread to the lungs.

Causes of lung cancer

Cigarette smoking is the main cause of about 90% of lung cancer cases in men and about 70% of them in women. The number of women that are diagnosed with lung cancer is rising. This is due to increasing numbers of women smoking. There are, however, other known factors that are associated with an increased risk of lung cancer:

* Dietary factors (deficient in vitamins, high in cholesterol).
* Occupational carcinogens (cancer-causing substances) such as industrial chemicals.
* Ionizing radiation.
* Exposure to radon gas (radioactive gas, found in increased amounts in mines).
* Genetic factors (inherited predisposition to developing lung cancer).

Symptoms of lung cancer

The symptoms of lung cancer are very non-specific. This is the reason that many patients with lung cancer present at an advanced stage of the disease. One factor hindering or delaying the early diagnosis of lung cancer is that the symptoms, such as cough, are common to other conditions.

The symptoms include: Breathlessness, cough, and chest pain, lethargy, and weight loss. All these symptoms are very common and are present in numerous other conditions. Even coughing up blood (hemoptysis), which is thought by many to be defining symptom of the condition, is not present in the majority of patients diagnosed with lung cancer.

A variety of investigative tools are used to confirm a diagnosis of lung cancer. These are:

* Chest X-ray. The majority of lung cancers are discovered after a patient goes to see their family physician with one or more of the symptoms mentioned. In the presence of such symptoms, particularly in smokers, a chest X-ray is mandatory. If the X-rays show either an abnormal shadowing or an obvious mass that is regarded non-specific but needs further investigation, you may be referred to a chest specialist, who may use a bronchoscope to look for cancerous growths in your bronchi.
* Fiber-optic bronchoscopy. The large air passages within the lungs are inspected, using a flexible fiber-optic camera. It is usually performed under local anesthesia.
* CT scanning. The patient lies flat and is passed slowly through a circular scanner. The scanner takes x-rays in slices 1 centimeter in thickness and usually 1 cm apart. With the aid of specialized computer software, the lungs can be viewed three dimensions.
* MRI scanning. Occasionally, this type of scan is used to assess invasion of the tumor into adjacent structures.
* Bone scans. A radioactive isotope is injected into the bloodstream and is taken up by the bones. Areas of the tumor spread show up as areas of increased uptake.
* Needle biopsy. If the tumor is not visible at bronchoscopy but is visible on the CT scan, a needle biopsy may be performed through the chest wall. Local anesthetic is applied to the skin and muscle of the chest wall and the needle is guided into the tumor using either conventional X-ray or CT scanning.
* Abdominal ultrasound. Used to look for tumor spread to the liver, it is the same type of scan used during pregnancy.

Progression of lung cancer

The outlook for patients with lung cancer depends on how far the tumor has spread before diagnose. The tumor may spread into adjacent structures, or it may spread into local lymph nodes within the chest.

Stages of the disease

1. Stage I – Tumor confined to the chest. No evidence of distant spread.
2. Stage II – Large tumor than stage I, or local lymph node enlargement. No evidence of distant spread.
3. Stage III A – more extensive lymph node enlargement. No spread outside the chest.
4. Stage III B – lymph node spread into the other side of the chest. No spread outside the chest.
5. Stage IV – Spread outside the chest, for example to the brain, bones, liver, adrenal glands (situated above the kidneys), or skin.

Treatment

The treatment of lung cancer depends upon the type of tumor, the stage of the disease at diagnosis and the general fitness of the patient. If the tumor is small and there is no evidence of spread to local lymph nodes, surgical removal of the tumor is usually performed. Chemotherapy is used in all other stages, and roughly 75% of tumors will respond to it. In patients who decline operation, or who are not fit for surgery but have stage I, II, IIIA disease, high dose radiotherapy is the treatment of choice. It involves bombarding the lung tumor with high-dose radiation aiming to kill all the cancer cells.

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