What to Expect in an Established Lung Cancer Screening Program
Lung cancer screening brings hope for early detection to many at high risk.
Lung cancer is the leading cause of cancer deaths in the US. More people die of lung cancer than die of the next four leading cancers combined: colon, breast, prostate, and pancreatic.
Five-year survival rates are less than 18% because lung cancer is usually discovered at a late stage when the chances for a cure are small. That's the bad news.
The good news is that we now have a screening test for lung cancer. Screening is done annually for people at high risk of lung cancer using a low dose CT (LDCT) scan to find lung cancer at an early stage before it causes any symptoms. Early-stage lung cancer has a good chance to be cured with surgery or, for patients who are not surgical candidates, stereotactic body radiotherapy. Late-stage lung cancer has a five-year survival rate of less than 5%. In the absence of screening, about 80% of lung cancers are diagnosed at a late stage.
The National Lung Screening Trail (NLST) showed a 20% reduction in mortality for people screened with LDCT for 3 rounds with a baseline scan and 2 annual scans, as compared to being screened with chest x-rays.
- Ages 55 – 77 (80 for private insurance),
- Current smoker need to have quit within the last 15 years
- ≥30 pack-year history of smoking (1 pack a day for 30 years or 2 packs a day for 15 years and so on)
In this high risk group, the risk of dying of lung cancer for women is at least twice her risk of dying of breast cancer
- For a 55 year old woman who qualifies for lung cancer screening (heavy smoker)
- Her breast cancer mortality on-going risk = 2.5%
- Her lung Cancer mortality on-going risk = 4.9% - this number is for an average smoker. To qualify for lung cancer screening requires a heavy smoking history so the risk will be even greater.
- So her relative risk of dying of lung cancer is at least 2 times that her risk of dying of breast cancer (RR = 4.9/2.5 = 2.0)
The risk for lung cancer is not the same for everyone in the high risk group. Some people are at higher risk than others because they have more risk factors for getting lung cancer. These risk factors include:
- A first degree relative diagnosed with lung cancer; mother, father, sister or brother, or child increases risk by about 2 times
- Having a history of cancer in the past increases risk by about 1.5 times
- African-American have about 1.5 times higher risk
- COPD or emphysema or chronic bronchitis increases risk by about 1.5 times
- Risk is increased the more cigarettes smoked, the longer a person smokes, if the person is still smoking, and reduced the longer it has been since former smokers quit.
- The risk of getting lung cancer also increases with age.
- Risk also increases with occupational exposure to asbestos, radon, cadmium, silica, diesel fuels or other carcinogens.
- Radon is the second leading cause of lung cancer. Having high radon levels in the home increases the risk of lung cancer.
Risk calculators, such as this one, can help assess individual risk levels. Radiation exposure for LDCT screening is about the same as for a mammogram. Follow-up diagnostic testing may increase radiation exposure.
There is a possibility that lung cancer screening will find a lung cancer that would never cause any problems. There is no reliable way of predicting the lung cancers that will not cause problems so patients may get treatment they don't really need. It is estimated that about 10% of lung cancers found during screening fall into this category.
No test is 100% perfect. It is possible a lung cancer that is there is not found during the screening exam, a false negative. In the NLST, this happened about 6% of the time.
About 20-25% of initial LDCTs will show something that needs follow-up. About 85-90% of the time these are not cancer (false positives). The follow-up is usually another LDCT in 1 to 6 months. In about 0.5% of cases, surgery will be done for a something that turns out not to be lung cancer. For subsequent annual LDCTs, about 10 to 15% return for follow-up in less than a year.
About 9% of the time the baseline (first) screening exam and about 2% of annual follow-on exams will show a finding outside of the lungs in areas such as the kidneys, liver, thyroid and adrenal glands. These "incidental findings" may require further evaluation.
In the International Early Lung Cancer Action Program a program screening high risk people for lung cancer using LDCTs, 80% of the people who were diagnosed with lung cancer were cured.
At Lahey Hospital & Medical Center (LHMC), for example, more than 4100 people have been screened for lung cancer; and more than 75% have been found at an early stage. An additional benefit of lung cancer screening programs is that it helps smokers quit smoking and former smokers to stay smoke free. In the LHMC lung cancer screening program, smoking cessation and smoking relapse rates were 2 to 3 times better than in the general population.
Lung cancer screening has the potential to change the lung cancer statistics and the lung cancer journey bringing hope to many at high risk. Radiologists play a key role in raising awareness and in implementing responsible screening programs.