LUNG CANCER

Incidence

It is reported that in 2005, carcinoma of the lung will account for 31% of cancer deaths in males and 27% of cancer deaths in females.

It is estimated that in 2005 there were 92,305 cases of lung cancers in men and 79,544 cases in women.

Age

Seventy percent of all lung cancer deaths occur between the ages of 55 and 74. However, recent trends indicate that both the incidence and mortality of lung cancer is increasing in younger age groups.

Sex

The incidence of lung cancer:

Males  > 70 per 100,000
Females > 22 per 100,000

It is approximately three times more common in men than females. However the incidence of lung cancer in females in increasing in epidemic proportions.

Cancer Death in Women

The incidence of female lung cancer continues to increase and has surpassed breast cancer as a leading cause of cancer deaths among women. Currently, carcinoma of the lung accounts for 12% of all new cancers in women and 27% of all cancer deaths.

Men

Lung cancer has been the leading cause of cancer deaths among males since 1955. However from 1955-1985 the incidence of lung cancer deaths among males has increased from 30 per 100,000 to greater than 70 per 100,000. In 2005 lung cancer accounted for 13% of all new cancers among males and 31% of all cancer deaths.

Countries

The countries with the highest incidence of lung cancer among males is the United Kingdom (90 per 100,000 males). The lowest incidence of lung cancer occurs in Asia and Africa. Rates for most of North America and Europe are between these two extremes. In general, the incidence of lung cancer in industrialized western countries is increased compared to third world countries. This difference is most likely attributable to increased cigarette smoking. However, other factors such as the presence of ceratin industries (chemical, petroleum and shipbuilding) and increased levels of air pollution may play a lesser role.

USA

The highest incidence of lung cancer in the United states, according to a 20 year review of mortality form all the cancers in the United States is in the northern urban areas and along the gulf and south Atlantic Coasts from Texas to Florida. Farming areas were found to have a lower incidence than other areas, including rural non-farm areas.

Etiology

Smoking

Lung cancer is largely attributable to environmental carcinogens. By far, the most important environmental carcinogen is tobacco smoke. Men began smoking cigarettes during World War I. The incidence of lung cancer among men began a rapid rise 20 years later. An identical but similar delayed pattern has been observed in women.

Today, the epidemiology of lung cancer is the epidemiology of smoking. Other factors are relatively of minor importance.

Carcinogens

Cigarette smoke contains a number of proven carcinogens in both the particulate and gaseous phase including:
-Aromatic Hydrocarbons
-Nitrosamines
-Nitrosonormicotine
-Polonium
-Arsenic

Synergic

Exposure to certain substances have a synergic effect in being causatively associated with the use of tobacco products in development of lung cancer.
-Asbestos
-Chloromethyl Ethers
-Mustard Gas
-Radioactive Ore

Host Factors

As with most illnesses, the development of disease depends on a complex interaction between the environment and the host. Specifically with lung cancer, host factors play a relatively minor role.
-Risk of Second Primary
-Associated Malignancies
-CLL
-Aryl Hydrocarbon Hydroxylase
-Scar Carcinoma
-Tuberculosis

Natural History

The natural history of Lung cancercan be described by breaking down its course of existence into a sequence of a few simple phases based on the way we experience the disease clinically.

Pre-Detectable

Carcinoma of the lung always passes through a pre-detectable phase, beginning with its biological onset (the development of the first frankly malignant cell) and beginning when the disease may first be shown to exist whether through sputum cytology or chest radiography. It has been claimed that by the time a tumor is 10 mm in diameter it has already doubled in size 30 times, contains at least one billion cells, and has completed three-fourths of its anticipated existence. It is likely that during the majority of a lung tumor's existence it will be undetectable by any currently available diagnostic technique.

Detectable-Asymptomatic

Most cases of lung carcinoma are felt to enter a phase in which presence of the disease is potentially demonstrable, yet continues to be without symptoms. The disease is detectable if:

·        
The tumor is radiographically evident (5-10 mm in diameter), or
Sputum is positive for malignant cells.

The duration of this "presymptomstic-detectable" phase is heavily dependent on the cell type involved and on location of the primary tumor. Sputum cytology can be positive for several years before symptoms occur in a progress from undetectable to unresectable within a few short months. Unfortunately, only about 5% of lung cancer diagnoses are made in this phase. These findings are typically made through incidental X-Ray findings during workup of an unrelated condition of through sputum and X-Ray screening of high-risk patients.

Symptomatic Phase

About 95% of all lung cancer diagnoses are made during the phase when the disease has become symptomatic. Carcinoma discovered at this point in its natural history is almost always well advanced. With very few but significant exceptions, symptomatic lung cancer carries poor prognosis. This is because the vast majority of symptoms in this disease are caused by either locally unresectable or metastatic tumor.

Symptoms Grouping

Carcinoma of the lung causes on astonishing variety of symptoms. Those which bring about the initial presentation as well as those which develop as the disease progresses are not only remarkably diverse, but vary widely between patients. It is not uncommon for the diagnosis to be made during workup of such conditions as Cushing's syndrome (due to ectopic ACTH production), or of neurological complaints found ultimately to be due to brain metastases! Therefore, in order to study the clinical manifestations of this disease in some productive way, it is helpful to group the symptoms lung cancer may cause into five general categories.

Primary Tumor

Endobronchial location of the tumor explains many of the symptoms related to primary tumor. If the primary is peripheral and the lesion is in the lung, often the symptoms related to primary tumor are absent.

• Cough
• Dyspnea
• Hemoptysis
• Pso-obstructive Pneumonia
• Increase in Sputum

Distant Metastasis

Several organs or organ systems clearly emerge as the most common sites of distant metastasis for lung carcinoma. These have great bearing on the clinical manifestations of the disease, and are frequently the cause of the clinical manifestations of the disease, and are frequently the cause of the patient's initial presentation!

• Brain
• Liver
• Bone
• Skin
• Adrenals
• Lymph Node

Paraneoplastic Syndrome

These are an ever-expanding set of intriguing clinical syndromes involving non-metastatic systemic effects which have been noticed to accompany malignant disease on occasion. Some are associated with a specific cell type; others have no such predilection. Most are felt to be biochemically mediated. Some are just plain mysteries.

• Endocrine
• Musculoskeletal/Cutaneous
• Hematologic
• Neuromuscular
• Cardiovascular Miscellaneous
• Hypertrophic Osteoarthropathy
• Clubbing
• Acanthosis Nigricans
• Thrombophlebitis
• ACTH
• ADH
• Hypercalcemia

Intrathoracic Spread

When carcinoma of the lung causes symptoms though intrathoracic spread, it tends to do so in only two primary ways:

• By Contiguity
• Nodal Metastasis

Whatever the mode of spread, most of the associated symptoms occur once the disease has reached either the chest wall or the mediastinum. If it was central, mediastinal problems tend to occur. If the tumor was located very inferior, diaphragmatic symptoms may be expected. If it began out in the periphery, chest wall problems are usually noted first.

Clinical problems that result from extension to the chest wall aren't difficult to understand. Since the parietal pleura is one of the few pain-sensitive structures in the area, this may be the first time the patient experiences pain. Pleural effusion is also a common condition related to this process. If the tumor happened to start near the apex of the lung, a syndrome knows as "Pancoast Tumor" may develop, involving complaints related to damage of CB-T1 roots.

Non-Specific

The following are non-specific symptoms due to tumor burden:

• Weight loss
• Malaise
• Loss of appetite

Staging

During the past years, numerous investigators have been endeavoring to establish a standard terminology that would accurately describe the extent of a cancer. One such staging system for lung cancer has been formulated by the Task Force on Lung Cancer of the American Joint Committee for Cancer Staging and End-Results Reporting (AJCF). The AJC staging system employs the T-N-M nomenclature . In this system, the letter T represents the primary tumor N regional node involvement, M.

T. Numerical Suffix Assignment

The criteria are:

·         Size

·         Proximity to Carina

·         Extent of Collapse

·         Invasion of surrounding structures

N Numerical Suffix Assignment

The first station lymph nodes are the intrapulmonary, peribronchial and hilar lymph nodes, which are contained within the visceral reflections. Second station lymph nodes are those in the mediastinum and may be paraesophageal, subcarinal, paratracheal, aortic or retrotracheal. Involvement of scalene, contra-lateral or extra-thoracic nodes is considered distant metastasis.

M Suffix Assignment

The metastatic status is signified by the letter "M" with subscripts O or 1 to indicate absence or presence of metastatic disease. "M1" signifies presence of metastasis in one or more distant organs. The common metastatic sites are Brain, Bone, Liver, Adrenal glands and subcutaneous tissue.

Group Staging

T, N and M combinations are used to group stage lung cancer. The staging is important in planning therapy and for estimating prognosis

Principles of Therapy

Therapeutic options consist of:

Surgery is the best option in:. 

Non-small cell cancer in stages 1, 2, 3a

Acceptable general condition as a surgical candidate 

In general, small cell cancer is not a surgical disease.

Radiation Therapy

If the general condition precludes the patient from being a surgical candidate, Radiation therapy is chosen. 

Palliative Radiation therapy has an important role for relief of symptoms in inoperable cases.

Chemotherapy

Chemotherapy is the treatment of choice for small cell cancer. Its role in NSCC is under investigation.

Supportive Care

One needs to consider the following  to determine the best option.

• Cell type
• Stage
• Clinical status

Prevention

• Lung cancer is a preventable disease. If cigarette consumption is stopped, we can probably prevent 99% of lung cancers. 
• As a physician, it is your obligation to set an example by not smoking and to advise patients not to smoke. 
• You can offer options to aid patients in quitting their habit.
• Nicotine chewing gum or patches
• Clinics which specialize in helping patients quit smoking
• Hypnotherapy
• Take an active role in bringing legislation to curb the use of cigarettes in public places. 
• Additionally, advertisements should be discontinued which encourage children to start the habit. 
• We probably should not attempt to ban cigarettes completely. It is unlikely to succeed, as we have learned from our past experience in trying to ban alcohol.