20-Year Survival Reaches 80 Percent in Patients Diagnosed Through Lung Cancer Screening

Findings from a 20-year international study show that patients diagnosed through annual low-dose computed tomography screening have long-term survival rates of up to 80%.

The researchers studied the International Early Lung Cancer Action Program (I-ELCAP), a prospective study with 87,416 participants, to examine lung cancer-specific survival.

Lung cancer, is the leading cause of cancer-related deaths worldwide. Currently, across all stages combined, lung cancer-specific 5-year survival is around 20%. Survival rates are higher at earlier stages. However, US data indicate that only 16% of lung cancers are detected early, and more than half of people with lung cancer die within a year of diagnosis.

What Is Low-Dose Lung CT?

For people at high risk of lung cancer because of long-term smoking, the current standard recommendation for early detection is annual low-dose computed tomography of the lungs. Previously, annual screening was recommended for people aged 55 with a 30 pack-year smoking history. Updated criteria introduced in 2021 classified everyone aged 50 with a 20 pack-year smoking history as being at high risk of lung cancer and recommended low-dose lung CT for them.

Note: A pack-year is defined as smoking an average of 20 cigarettes, or one pack, daily for one year. For example, smoking 1 pack a day for 20 years amounts to 20 pack-years, while smoking 2 packs a day for 10 years also amounts to 20 pack-years.

20-Year Survival Was 80% Among Participants in the Low-Dose CT Study

This large international study found an overall 20-year survival rate of 80% (95% CI, 77% - 83%) among 1,285 screening participants diagnosed with early-stage cancer. These are the highest survival rates reported for lung cancer to date. Of the 1,285 people diagnosed, 83% were reported to have stage 1 cancer.

For participants with tumours averaging 10 mm or less in diameter and pathological stage IA lung cancer, 20-year survival was 92% (95% CI, 87% - 96%).

These findings extend the results published in 2006 in NEJM, which showed 10-year survival of 80% with low-dose CT.

By contrast, 95% of Americans diagnosed with lung cancer around the time of the 2006 article who were not part of this study have now died of the disease.

When lung cancer symptoms appear, the cancer is usually advanced. Enrolling in an annual screening programme is therefore the best way to detect early-stage lung cancer, and low-dose lung CT is the most effective method for this purpose. Plain chest X-rays have not proved effective for early lung cancer detection. 

When a cancer is small enough to be surgically removed, patients can be effectively treated over the long term.

In the future, some blood tests known as liquid biopsies may replace low-dose lung CT. Until then, this appears to be the best available tool for early lung cancer screening.

The study also highlights the importance of conducting clinical research by collecting data prospectively. 

Findings Are "Very Promising"

This is one of the longest-running studies assessing low-dose CT screening. It is encouraging that the initial benefits persist over a longer observation period.

This supports evidence that lung cancer screening remains beneficial over longer observation periods. Many studies have had shorter follow-up, which is important to recognise.

As a reminder, lung cancer screening is recommended for people at high risk of lung cancer, meaning those aged 50-80 with a history of at least 20 pack-years of tobacco use.

Screening is currently limited to people at high risk. However, there is discussion about whether its benefits might extend to people exposed to asbestos or second-hand smoke, for example.

The greatest challenge now is screening those who actually meet the criteria: smoking rates are very high, yet very few people undergo this form of lung cancer screening.

The American Lung Association reports in a new publication that fewer than 6% of high-risk smokers undergo the recommended annual lung cancer screening.