Early Onset Lung Cancer – Prevalence, Causes, And Survival

We normally think of lung cancer as an affliction of elderly smokers however this isn’t always the case. The following article provides a brief overview of the prevalence, causes, and survival statistics for lung cancer in younger people.

Prevalence

Lung cancer before the age of 50 is relatively rare in the United States however more than 12,000 cases still occur annually, a rate of 4.2 per 100,000 individuals per year. A smoker has around a 1% chance of developing lung cancer before the age of 50 while a non-smoker’s chances are less than 1 in 1,000.

In the USA, lung cancer is the ninth most common form of cancer in the under 50 age group, accounting for around 6% of all cancers. The majority of lung cancer cases diagnosed in the young are adenocarcinomas, a form of non-small-cell lung cancer that arises from the glandular tissue of the lung.

The highest rate of lung cancer in the young is in Hungary with 10.9 cases per 100,000 per year in the under-50 age group. This is primarily due to a large number of heavy smokers in the country who often begin smoking at a very early age. A 1999 survey of secondary school students in Budapest, Hungary, found that a massive 46% of 15-18 year-olds were current smokers with almost a quarter of them smoking at least 11 cigarettes a day.

Lung cancer in childhood is extremely rare but not unheard of. In 2008, there were 25 cases of lung cancer in children aged under 15 in the USA and 1,144 cases worldwide. Childhood lung cancer rates are higher in developing countries however this may be the result of mis-diagnosis where cancer at another site has metastasized to the lung.

While lung cancer is more common in men than women overall, early-onset lung cancer actually occurs more often in women than men. In the under 45 age group, the female to male ratio of lung cancer is 1.14 to 1.

The incidence of lung cancer in the young has declined dramatically in the United States over the past half century. As can be seen from the graph below, the decline has been much greater in males than in females. In 1975, males aged under 50 were almost twice as likely to develop lung cancer as females. The gap has closed steadily over the last 30 years and in the early 2000s, the male rate actually dropped under the female rate.

Graph of lung cancer trends in the under 50s

Causes

The majority of lung cancer cases in the under 50 group occur in heavy smokers who began smoking in their teenage years. Around 15% of early-onset lung cancers occur in non-smokers.

Some studies have found a low median age of lung cancer in HIV infected individuals who smoke, suggesting that the combination of the two risk factors may hasten the development of lung cancer.

A high proportion of young females diagnosed with lung cancer are infected with Human papillomavirus (HPV), the findings are not fully explained by adjustment for smoking suggesting a role for the virus in the development of early-age lung cancer.

A study of young adults in Chile found an increased incidence of lung cancer (around 7 times greater) in individuals aged 30-49 who were exposed to arsenic in utero and in early childhood.

Exposure to second-hand smoke, asbestos, and radon gas in childhood have also been suggested as possible causes of early onset lung cancer.

Survival

Lung cancer in the young tends to be diagnosed at a later stage than lung cancer in older individuals. This is probably because lung cancer is rarely suspected in younger age groups leading to delays in diagnosis. Around 8% of lung cancers in the under 45 age group are stage-I at diagnosis compared to 15% of lung cancers in the over 45 age group. There is also some evidence that lung tumors in younger people tend to be faster growing and more aggressive than in older people.

Despite this, survival is significantly higher overall in younger lung cancer patients. 5-year survival rates in the USA are 21.6% in the 20-44 year age group compared to 15.5% overall.

Graph of lung cancer survival in the young