Lung cancer is the most common cause of cancer death in the U.S.- by a large margin..
Your personal risk of getting lung cancer depends upon a number of risk “factors”.
Sex In the past it was primarily a disease of men, but this is no longer true. Lung cancer now kills more women than any other cancer; more than breast, ovarian and colon cancer – combined.
Age: Lung cancer is very uncommon (less than 1%) under age 40, but increases steadily with advancing age.
Radiation: Historically, lung cancer was a very rare form of cancer. It was first described among radium miners in Central Europe. It is now known that radiation damage to chromosomes increases risk of lung cancer. This includes atomic bomb survivors, radiation workers and household exposure to radon. Radiation risks are much smaller than risk from exposure to cancer- causing substances (carcinogens) found in tobacco smoke.
Cigarette smoking: Cigarette smoking was first recognized as a cause of lung cancer in the 1930s. A formerly rare disease assumed epidemic proportions thereafter. Risk of lung cancer is related to the age of starting to smoke and the number of years of smoking as well as the amount of smoking i.e. number of packs smoked per day. This is sometimes summarized as “pack-years”. If you smoked one pack/day for 30 years it would equal 30 pack-years exposure.
Smoking cessation: It is important for your health that you quit smoking. Quitting stops DNA damage from inhaled carcinogens immediately and your risk of getting lung cancer will decrease compared to a person who keeps smoking. It is crucial to understand though that an ex-smoker continues at increased risk of lung cancer. Some maintain that risk becomes low 15 years after quitting, but this is not true. In Los Angeles, most ex-smokers operated on for lung cancer had quit more than 15 years earlier.
Emphysema and Chronic Obstructive Lung Disease (COPD):: Cigarette smoking also causes other disease, including chronic lung damage. People with emphysema have a substantially higher risk of lung cancer than smokers without emphysema.
Family History of lung cancer: is a known risk factor for lung cancer. This may be explained by the fact that children of smoking parents have a higher incidence of smoking.
Chemical carcinogens: Industrial workers exposed to asbestos have an increased risk of lung cancer as well as another cancer called mesothelioma. Workers exposed to arsenic, chromates and other industrial chemicals have increased risk of lung cancer.
Pneumonia Patients who have had an infection in the lung have a slightly increased risk of lung cancer.
Lung Fibrosis: Lung cancer is more common in people with a group of diseases classified as pulmonary fibrosis.
Prior tobacco-caused cancer: Individuals with a prior cancer of the lung have the highest risk of a second lung cancer. This risk is at least 20% I.e. 1 in 5 will have a second primary lung cancer during the next ten years. Risk is also very high among smokers who have had a prior cancer of the mouth, throat, larynx, esophagus and bladder.
Risk models: are used to try to estimate the risk of an individual. There are at least 10 such models in current use and some are available on the internet. In my opinion, the best is on a website at the University of Michigan. The problem is that none of the models looks at all risk factors and thus all potentially provide underestimates of risk.
The National Comprehensive Cancer Network (NCCN) recommends that individuals over the age of 50 who have smoked 20 pack-years or more are at increased risk of lung cancer and should consider screening. They set no upper age limit for those at high risk
There are two important remaining considerations.
Medicare/Medicaid eligibility: Currently Medicaid will pay for screening only for those age 55-77 who have smoked 30 pack-years or more and who quit less than 15 years earlier. Others who wish to be screened will have to pay out of pocket. The cost of a low-dose, non-contrast CT scan varies considerably between $100-500 in different centers.
Never-smokers and light-smokers are currently ineligible for screening. This is despite the fact that such individuals still have a substantial risk of lung cancer. Lung cancer in non-smokers is currently the sixth most lethal cancer in the U.S.. Lung cancer risk is substantially higher in persons with exposure to involuntary smoking so-called “second hand smoke”.
How high is the risk?
The National Lung Screen Trial (NLST study) detected lung cancer in 2.1 % of participants at six years, 1 in 50, but reappraisal at ten years showed a 6.7% incidence. That is 1 in 15. But this number is also too low.
A study at the University of Toronto in a high-risk group showed that CT detected lung cancer in 20% over a ten year period.
At City of Hope and New York’s Memorial Hospital studies have shown that lung cancer survivors have a 20% risk of a second lung over a decade. That is 1 in 5.
The bottom line is that if you are a middle-aged or senior adult who is a smoker or ex-smoker, you are at substantial (10-15%) risk of lung cancer, 1 in 7 to 1 in 10, particularly if you have other risk factors as described above.
Why be screened? As discussed earlier, if you get lung cancer and it is diagnosed only after you present to your doctor’s office with symptoms, the chances are that the cancer will be advanced and chance of cure will be small.
Does screening lower the risk of dying from lung cancer? Yes.
This will be discussed in future blogs.