Lungs and Lung Cancer

Lungs : Introduction

Human lungs are two spongy organs located on each side of the heart. During inhalation, air flows from the nose or mouth through the pharynx (throat) and larynx (which contain the vocal cords) into the trachea (wind pipe). The trachea divides into two bronchi, which direct air into the right and left lungs.

Within the lungs, the bronchi divide into several smaller bronchioles. Air flows from bronchioles into tiny air sacs, called alveoli. A group of alveoli is referred to as a lobule. Lobules are, in turn, grouped into lobes. The left lung contains two lobes, whereas the right contains three.

 

A network of tiny blood vessels, called capillaries, surrounds the alveoli. The lining of these blood vessels is so thin that oxygen and carbon dioxide can move between the capillaries and the alveoli. Carbon dioxide diffuses from the capillaries into the alveoli and is released from the body during exhalation. Oxygen diffuses in the opposite direction, from the alveoli into the blood, and is carried throughout the body by the circulatory system.

Most lung cancers begin in epithelial cells lining the bronchi. Cancers that develop in epithelial cells are known as carcinomas

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Lung Cancer : Introduction

Lung cancer currently  ranks as the leading cause of cancer related deaths in men and 

women. Although continuing to decline in men, incidence rates remain level in women

following an increase throughout the1990's. Trends in lung cancer related death reflect

trends in smoking over the past several decades. In2010, the American Cancer Society

estimates 222,520 new cases will be diagnosed and 157,300 deaths 

due to lung cancer will occur in the United States.

History of Lung Cancer

Cancer of the lung was nearly nonexistent in the early 1900's. By the 
middle of the 20th century, however, an epidemic became apparent 
throughout the U.S. and the rest of the world. This dramatic increase 
correlated with the widespread prevalence of cigarette smoking. The 
tobacco industry had largely multiplied its production immediately 
prior to WWI. The early part of the epidemic correlated with the 
typical 20 to 30-year lagging period between initiation of smoking and 
the actual tumor formation. Despite denial from the tobacco companies 
the correlation was conclusively established in 1950. The tobacco 
companies continued to maintain that cigarette smoking was not 
addictive and did not cause cancer. Tobacco companies remain the most 
profitable business in the world. 
Lung cancer is not a single neoplasm but a group of aggressive 
malignant tumors of the lower respiratory tract and are by far the most 
lethal of human tumors for men in the world and since 1987 it exceeded 
breast cancer as the leading cancer cause of death in women in the U.S. 
(68,800 vs. 39,800 respectively in 2004), a fact not well known among 
women and many health professionals. Women now account for 40% of all 
lung cancer cases. The reason is not known but women who smoke are 
more than twice as likely as male smokers to develop lung cancer. Even 
years after smokers of either gender quit, their risk of acquiring lung 
cancer stays high. The risk of second hand smoking is real and women 
are at a significantly higher risk.
The annual incidence and mortality rate of lung cancer has increased 
more than any other malignancy in the last decade. In 1950 there were 
18,318 deaths from lung cancer in the United States. The American 
Cancer Society estimates that 172,000 new cases of cancer of the lung 
will be diagnosed this year, accounting for 13% of all 1.3 million new 
cancer cases expected, and less than 15% of these patients will 
survive. It also estimates that there will be over 160,000 deaths as 
a result of cancer of the lung in 2004, accounting for 28% of all 
cancer mortality. Lung cancer alone accounts for more cancer deaths 
than the combined number of the next four more common causes of cancer 
death in America. Despite great advances in medicine in the last 40 
years, the overall 5-year survival rate of cancer of the lung of only 
15% has remained strikingly unchanged. In contrast, in all types of 
cancer that have early detection programs, the 5-year survival rate 
significantly increased in the last 20 years. Cancer of the colon 
improved from 50 to 62%, breast cancer from 75 to 86%, and cancer of 
the prostate from 67 to 97%. Unfortunately, the current official 
position of the American Cancer Society is against screening for cancer 
of the lung, even among high risk individuals, despite the fact that 
the 5-year survival rate of early staged cancer of the lung is 67% 
after surgical removal, compared with the commonly currently diagnosed 
symptomatic patients who usually present with advanced stages and have 
a less than 10% 5-year survival rate. 
Public perception that patients with lung cancer are to blame for their 
disease, lack of awareness and poor patient advocacy has created 
disparity with other less common causes of cancer death that are 
relatively better funded. Of interest over half of patients with lung 
cancer diagnosed today are never-smokers or ex-smokers and many of them 
victims of second hand smoking, of those particularly affected are 
women. An effective fight against cancer of the lung will require 
prevention, early detection programs and early intervention. Lung 
cancer screening must be made a public health priority, funds certainly 
exist from the tobacco companies settlement.