Lungs Cancer

What is lung cancer?

Cancer of the lung, like all cancers, results from an abnormality in the body's basic unit of life, the cell. Normally, the body maintains a system of checks and balances on cell growth so that cells divide to produce new cells only when new cells are needed. Disruption of this system of checks and balances on cell growth results in an uncontrolled division and proliferation of cells that eventually forms a mass known as a tumor.
Tumors can be benign or malignant; when we speak of "cancer," we are referring to those tumors that are malignant. Benign tumors usually can be removed and do not spread to other parts of the body. Malignant tumors, on the other hand, grow aggressively and invade other tissues of the body, allowing entry of tumor cells into the bloodstream or lymphatic system and then to other sites in the body. This process of spread is termed metastasis; the areas of tumor growth at these distant sites are called metastases. Since lung cancer tends to spread or metastasize very early after it forms, it is a very life-threatening cancer and one of the most difficult cancers to treat. While lung cancer can spread to any organ in the body, certain organs -- particularly the adrenal glands, liver, brain, and bone -- are the most common sites for lung cancer metastasis.
The lung also is a very common site for metastasis from tumors in other parts of the body. Tumor metastases are made up of the same type of cells as the original (primary) tumor. For example, if prostate cancer spreads via the bloodstream to the lungs, it is metastatic prostate cancer in the lung and is not lung cancer.
The principal function of the lungs is to exchange gases between the air we breathe and the blood. Through the lung, carbon dioxide is removed from the bloodstream and oxygen from inspired air enters the bloodstream. The right lung has three lobes, while the left lung is divided into two lobes and a small structure called the lingula that is the equivalent of the middle lobe on the right. The major airways entering the lungs are the bronchi, which arise from the trachea. The bronchi branch into progressively smaller airways called bronchioles that end in tiny sacs known as alveoli where gas exchange occurs. The lungs and chest wall are covered with a thin layer of tissue called the pleura.
Lung cancer picture

Lung cancers can arise in any part of the lung, but 90%-95% of cancers of the lung are thought to arise from the epithelial cells, the cells lining the larger and smaller airways (bronchi and bronchioles); for this reason, lung cancers are sometimes called bronchogenic cancers or bronchogenic carcinomas. (Carcinoma is another term for cancer.) Cancers also can arise from the pleura (called mesotheliomas) or rarely from supporting tissues within the lungs, for example, the blood vessels.

Signs and symptoms

Symptoms that may suggest lung cancer include:

• dyspnea (shortness of breath)
• hemoptysis (coughing up blood)
• chronic coughing or change in regular coughing pattern
• wheezing
• chest pain or pain in the abdomen
• cachexia (weight loss), fatigue, and loss of appetite
• dysphonia (hoarse voice)
• clubbing of the fingernails (uncommon)
• dysphagia (difficulty swallowing).

Causes

The main causes of any cancer include carcinogens (such as those in tobacco smoke), ionizing radiation, and viral infection. This exposure causes cumulative changes to the DNA in the tissue lining the bronchi of the lungs (the bronchial epithelium). As more tissue becomes damaged, eventually a cancer develops.
Smoking
Radon gas
Asbestos
Viruses
Particulate matter

Prevention is the most cost-effective means of fighting lung cancer. While in most countries industrial and domestic carcinogens have been identified and banned, tobacco smoking is still widespread. Eliminating tobacco smoking is a primary goal in the prevention of lung cancer, and smoking cessation is an important preventive tool in this process. Of utmost importance are prevention programs that target the young. In 1998 the Master Settlement Agreement entitled 46 states in the USA to an annual payout from the tobacco companies.Between the settlement money and tobacco taxes, each state's public health department funds their prevention programs, although none of the states are living up to the Center for Disease Control's recommended amount by spending 15 percent of tobacco taxes and settlement revenues on these prevention efforts.
Policy interventions to decrease passive smoking in public areas such as restaurants and workplaces have become more common in many Western countries, with California taking a lead in banning smoking in public establishments in 1998. Ireland played a similar role in Europe in 2004, followed by Italy and Norway in 2005, Scotland as well as several others in 2006, England in 2007, France in 2008 and Turkey in 2009. New Zealand has banned smoking in public places as of 2004. The state of Bhutan has had a complete smoking ban since 2005. In many countries, pressure groups are campaigning for similar bans. In 2007, Chandigarh became the first city in India to become smoke-free. India introduced a total ban on smoking at public places on Oct 2 2008.
Arguments cited against such bans are criminalisation of smoking, increased risk of smuggling, and the risk that such a ban cannot be enforced.
The long-term use of supplemental multivitamins—such as vitamin C, vitamin E, and folate—does not reduce the risk of lung cancer. Indeed long-term intake of high doses of vitamin E supplements may even increase the risk of lung cancer.The World Health Organization has called for governments to institute a total ban on tobacco advertising to prevent young people from taking up smoking. They assess that such bans have reduced tobacco consumption by 16% where already instituted

Treatment

Main article: Treatment of lung cancer

Treatment for lung cancer depends on the cancer's specific cell type, how far it has spread, and the patient's performance status. Common treatments include palliative care, surgery, chemotherapy, and radiation therapySurgery

Main article: Lung cancer surgery

If investigations confirm lung cancer, CT scan and often positron emission tomography (PET) are used to determine whether the disease is localized and amenable to surgery or whether it has spread to the point where it cannot be cured surgically.

Blood tests and spirometry (lung function testing) are also necessary to assess whether the patient is well enough to be operated on. If spirometry reveals poor respiratory reserve (often due to chronic obstructive pulmonary disease), surgery may be contraindicated.
Surgery for lung cancer has an operative death rate of about 4.4%, depending on the patient's lung function and other risk factors. In non-small-cell lung carcinoma, surgery is usually only an option if the cancer is limited to one lung, up to stage IIIA. This is assessed with medical imaging (computed tomography, positron emission tomography). A sufficient preoperative respiratory reserve must be present to allow adequate lung function after the tissue is removed.
Procedures include wedge resection (removal of part of a lobe), segmentectomy (removal of an anatomic division of a particular lobe of the lung), lobectomy (one lobe), bilobectomy (two lobes), or pneumonectomy (whole lung). In patients with adequate respiratory reserve, lobectomy is the preferred option, as this minimizes the chance of local recurrence. If the patient does not have enough functional lung for this, wedge resection may be performed. Radioactive iodine brachytherapy at the margins of wedge excision may reduce recurrence to that of lobectomy.
Video-assisted thoracoscopic surgery and VATS lobectomy have allowed for minimally invasive approaches to lung cancer surgery that may have the advantages of quicker recovery, shorter hospital stay and diminished hospital costs.
Early studies suggested that small-cell lung carcinoma (SCLC) fared better when treated with chemotherapy and/or radiation than when treated surgically. While this approach to treating SCLC remains the current standard of care, the role of surgery in SCLC is being reconsidered, recent reviews indicating that surgery might improve outcomes when added to chemotherapy and radiation in early stage SCLCand combined forms of SCLC and NSCLC.
Radiotherapy
Radiotherapy is often given together with chemotherapy, and may be used with curative intent in patients with non-small-cell lung carcinoma who are not eligible for surgery. This form of high intensity radiotherapy is called radical radiotherapy. A refinement of this technique is continuous hyperfractionated accelerated radiotherapy (CHART), in which a high dose of radiotherapy is given in a short time period. For small-cell lung carcinoma cases that are potentially curable, chest radiation is often recommended in addition to chemotherapy. The use of adjuvant thoracic radiotherapy following curative intent surgery for non-small-cell lung carcinoma is not well established and is controversial. Benefits, if any, may only be limited to those in whom the tumor has spread to the mediastinal lymph nodes.
For both non-small-cell lung carcinoma and small-cell lung carcinoma patients, smaller doses of radiation to the chest may be used for symptom control (palliative radiotherapy). Unlike other treatments, it is possible to deliver palliative radiotherapy without confirming the histological diagnosis of lung cancer.
Brachytherapy (localized radiotherapy) may be given directly inside the airway when cancer affects a short section of bronchus.It is used when inoperable lung cancer causes blockage of a large airway.
Patients with limited-stage small-cell lung carcinoma are usually given prophylactic cranial irradiation (PCI). This is a type of radiotherapy to the brain, used to reduce the risk of metastasis. More recently, PCI has also been shown to be beneficial in those with extensive small-cell lung cancer. In patients whose cancer has improved following a course of chemotherapy, PCI has been shown to reduce the cumulative risk of brain metastases within one year from 40.4% to 14.6%.Recent improvements in targeting and imaging have led to the development of extracranial stereotactic radiation in the treatment of early-stage lung cancer. In this form of radiation therapy, very high doses are delivered in a small number of sessions using stereotactic targeting techniques. Its use is primarily in patients who are not surgical candidates due to medical comorbidities.

Chemotherapy

The chemotherapy regimen depends on the tumor type.

Small-cell lung carcinoma

Even if relatively early stage, small-cell lung carcinoma is treated primarily with chemotherapy and radiation. In small-cell lung carcinoma, cisplatin and etoposide are most commonly used. Combinations with carboplatin, gemcitabine, paclitaxel, vinorelbine, topotecan, and irinotecan are also used. Celecoxib showed a potential signal of response in a small study.
Non-small-cell lung carcinoma
Primary chemotherapy is also given in advanced and metastatic non-small-cell lung carcinoma.
Testing for the molecular genetic subtype of non-small-cell lung cancer may be of assistance in selecting the most appropriate initial therapy For example, mutation of the epidermal growth factor receptor gene may predict whether initial treatment with a specific inhibitor or with chemotherapy is more advantageous.
Advanced non-small-cell lung carcinoma is often treated with cisplatin or carboplatin, in combination with gemcitabine, paclitaxel, docetaxel, etoposide, or vinorelbine Bevacizumab improves results in non-squamous cancers treated with paclitaxel and carboplatin in patients less than 70 years old who have reasonable general performance status.
Pemetrexed has been studied extensively in non-small-cell lung cancer, with numerous studies since 1995. For adenocarcinoma and large-cell lung cancer, cisplatin with pemetrexed was more beneficial than cisplatin and gemcitabine; squamous cancer had the opposite results. As a consequence, subtyping of non-small lung cancer histology has become more important.
Bronchoalveolar carcinoma is a subtype of non-small-cell lung carcinoma that may respond to gefitinib and erlotinib

Maintenance therapy

In advanced non-small-cell lung cancer there are several approaches for continuing treatment after an initial response to therapy. Switch maintenance changes to different medications than the initial therapy and can use pemetrexed, erlotinib, and docetaxel, although pemetrexed is only used in non-squamous NSCLC.Adjuvant chemotherapy
Adjuvant chemotherapy refers to the use of chemotherapy after apparently curative surgery to improve the outcome. In non-small-cell lung cancer, samples are taken during surgery of nearby lymph nodes. If these samples contain cancer, the patient has stage II or III disease. In this situation, adjuvant chemotherapy may improve survival by up to 15%.Standard practice has often been to offer platinum-based chemotherapy (including either cisplatin or carboplatin). However, the benefit of platinum-based adjuvant chemotherapy was confined to patients who had tumors with low ERCC1 (excision repair cross-complementing 1) activity.
Adjuvant chemotherapy for patients with stage IB cancer is controversial, as clinical trials have not clearly demonstrated a survival benefit. Trials of preoperative chemotherapy (neoadjuvant chemotherapy) in resectable non-small-cell lung carcinoma have been inconclusive^.

Interventional radiology

Radiofrequency ablation should currently be considered an investigational technique in the treatment of bronchogenic carcinoma. It is done by inserting a small heat probe into the tumor to kill the tumor cells.Palliative care
In a 2010 study of patients with metastatic non–small-cell lung cancer, "early palliative care led to significant improvements in both quality of life and mood. As compared with patients receiving standard care, patients receiving early palliative care had less aggressive care at the end of life but longer survival" (increased by 3 months).
Other studies in advanced cancer also found benefit from palliative care, or found hospice involvement to be beneficial. These approaches allow additional discussion of treatment options and provide opportunities to arrive at well-considered decisions and may avoid unhelpful but expensive care at the end of life.
Chemotherapy may be combined with palliative care in the treatment of the non-small-cell lung cancer. In advanced NSCLC, a 1994 meta-analysis found that appropriate chemotherapy improved average survival over supportive care alone,as well as improving quality of life.With adequate physical fitness, maintaining chemotherapy during lung cancer palliation offers a 1.5 to 3 months prolongation of survival, symptomatic relief and an improvement in quality of life, with better results seen with modern agents.Since 2008, the NSCLC Meta-Analyses Collaborative Group has recommended that if the recipient wants and can tolerate treatment then chemotherapy should be considered in advanced NSCLC.