Causes

Smoking

The incidence of lung cancer is strongly correlated with cigarette smoking, with about 90% of lung cancers are due to tobacco use.

The risk of lung cancer increases with the number of cigarettes smoked over time; Tobacco smoke contains chemical compounds, many of which have been shown to be cancer causing. The two primary carcinogens in tobacco smoke are chemicals known as nitrosamines and polycyclic aromatic hydrocarbons.

Passive smoking

Passive smoking, or the inhalation of tobacco smoke from other smokers sharing living is also an established risk factor for the development of lung cancer. Research has shown that nonsmokers who reside with a smoker have a increase in risk for developing lung cancer when compared with other nonsmokers.

Air pollution

Air pollution from vehicles, industry, and power plants can raise the likelihood of developing lung cancer in exposed individuals.

Types

Lung cancers, also known as bronchogenic carcinomas are broadly classified into two types: small cell lung cancers (SCLC) and non-small cell lung cancers (NSCLC).SCLC comprise about 20% of lung cancers and are the most aggressive and rapidly growing of all lung cancers. SCLC are strongly related to cigarette smoking.

NSCLC are the most common lung cancers, accounting for about 80% of all lung cancer Adenocarcinomas are the most commonly seen type of NSCLC .

Squamous cell carcinomas were formerly more common than adenocarcinoma; at present, they account for about 30% of NSCLC.

Signs and symptoms

A person with lung cancer may have the following kinds of symptoms:

No symptoms :

In up to 25% of people who get lung cancer, the cancer is first discovered on a routine chest X-ray or CT scan as a solitary small mass sometimes called a coin lesion. These patients often report no symptoms at the time the cancer is discovered.

Symptoms related to the cancer :

The growth of the cancer and invasion of lung tissues leads  to symptoms such as cough, shortness of breath, wheezing, chest pain, and coughing up blood (hemoptysis).

Pancoast's syndrome

If the cancer has invaded nerves, it may cause shoulder pain that travels down the outside of the arm  called  as Pancoast's syndrome)

Invasion of the esophagus may lead to difficulty swallowing (dysphasia).

Symptoms related to metastasis: Lung cancer that has spread to the bones may produce excruciating pain at the sites of bone involvement.

Danger signs of lung cancer

A new persistent cough or worsening of an existing chronic cough

Blood in the sputum,

Persistent bronchitis or repeated respiratory infections

Chest pain

Unexplained weight loss and/or fatigue and/or breathing difficulties such as shortness of breath or wheezing.

Diagnosis of Lung Cancer

The history and physical examination may reveal the presence of symptoms or signs that are suspicious for lung cancer. doctors may detect signs of  breathing difficulties, airway obstruction, or infections in the lungs.

Cyanosis, a bluish color of the skin and the mucous membranes due to insufficient oxygen in the blood, that suggests compromised function of the lung.

Changes in the tissue of the nail beds, known as clubbing, may also indicate lung disease.

Chest Xray

The chest X-ray is the most common first diagnostic step when any new symptoms of lung cancer are present.

Chest X-rays may reveal suspicious areas in the lungs but cannot determine if these areas are cancerous

 In particular, calcified nodules in the lungs or benign tumors called hamartomas may be identified on a chest X-ray.

CT scan of chest

A CT  (computerized  tomography scan)  scan of the chest may be ordered when X-rays do not show an abnormality or do not yield sufficient information about the extent or location of a tumor.

One advantage of CT scans is that they are more sensitive than standard chest X-rays in the detection of lung nodules.

Sometimes intravenous contrast material is given prior to the procedure to help delineate the organs and their positions.

A CT scan exposes the patient to a minimal amount of radiation.

Side effects of CT scan

The most common side effect is an adverse reaction to intravenous contrast material that may have been given prior to the procedure.

There may be resulting itching, a rash, that generally disappear quickly MRI (Magnetic resonance imaging)

Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) scan is ordered when precise detail about a tumor's location is required.

The image and resolution produced by MRI is quite detailed and can detect tiny changes of structures within the body.

There are no known side effects of MRI scanning, and there is no exposure to radiation.

Contraindications Of MRI

People with heart pacemakers, metal implants, artificial heart valves, and other surgically implanted structures cannot be scanned with an MRI because of the risk that the magnet may move the metal parts of these structures

Positron Emission Tomography

Positron emission tomography (PET) scanning is a specialized imaging technique that uses short-lived radioactive drugs to produce three-dimensional colored images of those substances in the tissues within the body.

PET scans can determine whether a tumor tissue is actively growing and can aid in determining the type of cells within a particular tumor.

Bone Scan

Doctors may order a bone scan to determine whether a lung cancer has metastasized to the bones.

Sputam Cytology

The diagnosis of lung cancer always requires confirmation of malignant cells by a pathologist, even when symptoms and X-ray studies are suspicious for lung cancer.

The simplest method to establish the diagnosis is the examination of sputum under a microscope. This is the most risk-free and inexpensive tissue diagnostic procedure, but its value is limited since tumor cells will not always be present in sputum even if a cancer is present.

Bronchoscopy

Examination of the airways by bronchoscopy may reveal areas of tumor that can be sampled by biopsy for diagnosis .

Needle biopsy

Fine needle aspiration cytology (FNAC) through the skin, most commonly performed with radiological imaging for guidance, may be useful in retrieving cells for diagnosis from tumor nodules in the lungs.

Needle biopsies are particularly useful when the lung tumor is peripherally located .

Thoracentesis : Sometimes lung cancers involve the lining tissue of the lungs called pleura and lead to an accumulation of fluid in the space between the lungs and pleura called a pleural effusion.

Treatment of lung cancer

Treatment for lung cancer can involve

1. Surgical removal of the cancer,

2. Chemotherapy,

3. Radiation therapy, as well as combinations of these treatments

Surgery:

Surgical removal of the tumor is generally performed for limited-stage (stage I or sometimes stage II) NSCLC and is the treatment of choice for cancer that has not spread beyond the lung. The surgical procedure chosen depends upon the size and location of the tumor.

About 10%-35% of lung cancers can be removed surgically, but removal does not always result in a cure, since the tumors may already have spread and can recur at a later time

Surgeons must open the chest wall and may perform

1.  A wedge resection of the lung which means removal of a portion of one lobe.

2.  A lobectomy which means removal of one lobe.

3.  A pneumonectomy which means removal of an entire lung.

4.  Sometimes lymph nodes in the region of the lungs are also removed  Surgery for lung cancer is a major surgical procedure that requires general anesthesia, hospitalization, and follow-up care for weeks to months.

Radiation:

Indications of radiation therapy

Radiation therapy may be given as curative therapy, palliative therapy or as adjuvant therapy in combination with surgery or chemotherapy.

Radiation therapy may be employed as a treatment for both NSCLC and SCLC.

Radiation therapy uses high-energy X-rays to kill dividing cancer cells.Radiation therapy does not carry the risks of major surgery, but it can have unpleasant side effects like fatigue and lack of energy.

Chemotherapy:

Both NSCLC and SCLC may be treated with chemotherapy.

Chemotherapy refers to the administration of drugs that stop the growth of cancer cells by killing them or preventing them from dividing

Chemotherapy may be given alone, as an adjuvant to surgical therapy, or in combination with radiotherapy.  The class of drugs known as the platinum-    based drugs has been the most effective in treatment of lung cancers.

Treatment of recurrence:

Lung cancer that has returned following treatment with surgery, chemotherapy, and/or radiation therapy is called recurrent or relapsed.

If a recurrent cancer is confined to one site in the lung, it may be treated with surgery. A type of chemotherapy referred to as second-line chemotherapy is  used to treat recurrent cancers that have previously been treated with chemotherapy, and a number of second-line chemotherapeutic regimens have been  proven effective at prolonging survival.

Targeted therapy:

One alternative to standard chemotherapy is the drug erlotinib also called as Tarceva which may be used in patients with NSCLC who are not   responding   to chemotherapy.

It is called  as targeted drug, a drug that more specifically targets cancer cells. Erlotinib targets a protein called the epidermal growth factor receptor (EGFR) that helps cells to divide.

This protein is found at abnormally high levels on the surface of some types of cancer cells mostly non-small cell lung cancer.

Photodynamic therapy (PDT):

One newer therapy used for lung cancer is photodynamic therapy.

In photodynamic treatment, a photosynthesizing agent such as a porphyrin, occurring is injected into the bloodstream a few hours prior to surgery.

During this time, the agent deposits itself selectively in rapidly growing cells such as cancer cells.

The physician applies a certain wavelength of light to the site of the cancer and  surrounding tissues.

The energy from the light activates the photosensitizing agent, causing the production of a toxin that destroys the tumor cell

Research is ongoing to further determine the effectiveness of PDT in lung cancer.

Radiofrequency ablation

Radiofrequency ablation is being studied as an alternative to surgery, particularly in cases of early stage lung cancer.

Prognosis

The prognosis of lung cancer refers to the chance for cure and is dependent upon where the cancer is localized, the size of the cancer, the presence of symptoms, the type of lung cancer, and the overall health status of the patient.

SCLC has the most aggressive growth of all lung cancers, with a survival time of only two to four months after diagnosis when untreated. SCLC is also the type of lung cancer most responsive to radiation therapy and chemotherapy. 

 In NSCLC, results of standard treatment are generally poor. However, in stage I cancers that can be completely removed, five-year survival approaches 75%. Radiation therapy can produce a cure in a small minority of patients with NSCLC .

The overall prognosis for lung cancer is poor when compared with some other cancers.

Prevention of lung cancer

Smoking cessation is the most important measure that can prevent lung cancer.

Many products, such as nicotine gum, nicotine sprays, or nicotine inhalers, may be helpful to people trying to quit smoking.

Minimizing exposure to passive smoking is also an effective preventive measure

Methods that allow early detection of cancers, such as the helical low-dose CT scan, may also be of value in the identification of small cancers that can be cured by surgical resection and prevention of widespread, incurable metastatic cancer..