Lung cancer is uncontrolled cell growth that starts in the tissues of the lungs, typically in the cells lining the air passages. It is the leading cause of cancer death worldwide, but survival rates have improved significantly in recent years, particularly when the disease is caught early. The five-year survival rate for lung cancer found before it spreads beyond the lung is 65.5%, compared to just 10.5% when it has already reached distant organs.
The Two Main Types
Lung cancer falls into two broad categories based on how the cells look under a microscope. Non-small cell lung cancer (NSCLC) accounts for roughly 85% of all cases. Small cell lung cancer (SCLC) makes up the remaining 15% and tends to grow and spread more aggressively.
NSCLC includes several subtypes, the most common being adenocarcinoma (which starts in the cells that produce mucus), squamous cell carcinoma (which starts in the flat cells lining the airways), and large cell carcinoma. These subtypes matter because they respond differently to treatment. Adenocarcinoma, for instance, is the most common form in both smokers and non-smokers and is the type most likely to carry specific genetic changes that can be targeted with newer therapies.
SCLC is defined by its small, round cells that divide rapidly. It is strongly linked to smoking and is rarely seen in people who have never smoked. Because it grows so quickly, it often has already spread by the time it’s diagnosed, which changes the treatment approach considerably.
Symptoms to Recognize
Lung cancer often produces no symptoms in its earliest stages, which is one reason it’s frequently caught late. When symptoms do appear, they typically include a new cough that won’t go away, chest pain, shortness of breath, wheezing, or hoarseness. Coughing up blood, even a small amount, is a particularly important warning sign.
When lung cancer spreads to other parts of the body, the symptoms shift. Bone pain, persistent headaches, unexplained weight loss, loss of appetite, and swelling in the face or neck can all signal advanced disease. None of these symptoms are unique to lung cancer, which is part of what makes early detection challenging.
Causes and Risk Factors
Smoking is the dominant cause. Most cases of lung cancer can be attributed to tobacco use, and quitting reduces the risk over time. But smoking is not the only cause, and roughly 10 to 20 percent of lung cancers occur in people who have never smoked.
Radon, a naturally occurring radioactive gas that seeps into homes through cracks in foundations, is the second leading cause. The EPA recommends taking action when indoor radon levels reach 4 pCi/L or higher. To put the risk in perspective: out of 1,000 people who never smoked but were exposed to radon at 4 pCi/L over a lifetime, about 7 could develop lung cancer. At five times that level (20 pCi/L), the number jumps to about 36 out of 1,000. Radon test kits are inexpensive and widely available at hardware stores.
Other risk factors include exposure to asbestos, air pollution, secondhand smoke, and a family history of lung cancer. It’s worth noting that mesothelioma, a cancer sometimes confused with lung cancer, is a distinct disease. Mesothelioma starts in the thin lining around the lungs (the pleura) rather than inside the lung tissue itself, and its primary cause is asbestos exposure rather than smoking.
Genetic Changes That Drive Growth
Many lung cancers, especially adenocarcinomas, are driven by specific genetic mutations that act like a stuck accelerator pedal, telling cells to keep dividing. In a large study of nearly 6,600 lung cancers, 46% of adenocarcinomas had mutations in a gene called EGFR, about 9% had KRAS mutations, and about 7% had a rearrangement in a gene called ALK.
These mutations matter to patients because they open the door to targeted therapies: drugs designed to block the specific protein that’s fueling the cancer’s growth. If your tumor carries one of these changes, treatment can be more precise and often more effective than traditional chemotherapy alone. This is why doctors now routinely test lung cancer tissue for genetic mutations before choosing a treatment plan.
How It’s Diagnosed
The path to a lung cancer diagnosis typically starts with imaging. A low-dose CT scan (LDCT) can detect small nodules in the lungs long before they cause symptoms. If a scan reveals something suspicious, additional imaging such as a PET scan may follow to determine whether the nodule is active and whether the cancer has spread.
A biopsy, where a small tissue sample is removed and examined under a microscope, is the only way to confirm a lung cancer diagnosis. This can be done through a needle inserted through the chest wall, a bronchoscope threaded through the airways, or sometimes during surgery. It’s common for screening to turn up spots on the lung that look concerning but turn out to be harmless. These false positives can cause anxiety and lead to additional testing, but they’re a well-known part of the screening process.
Who Should Be Screened
The U.S. Preventive Services Task Force recommends annual lung cancer screening with LDCT for adults aged 50 to 80 who have a 20 pack-year smoking history and either currently smoke or quit within the past 15 years. A pack-year means smoking one pack per day for one year, so someone who smoked two packs a day for 10 years would meet the 20 pack-year threshold.
Screening should stop once a person has been smoke-free for 15 years or develops a health condition that would make treatment impractical. These guidelines exist because screening works best in people whose risk is high enough that the benefits of early detection outweigh the downsides of potential false alarms and follow-up procedures.
Stages and What They Mean
Lung cancer is staged from I to IV based on tumor size, whether cancer has reached nearby lymph nodes, and whether it has spread to distant organs. The staging system uses 1-centimeter intervals for smaller tumors: a tumor 1 cm or smaller is classified differently from one that’s 2 cm, which matters because even small differences in size correlate with different outcomes.
Stage I means the cancer is small and confined to the lung. Stage II involves a slightly larger tumor or spread to nearby lymph nodes. Stage III means the cancer has reached lymph nodes farther from the original tumor, potentially in the center of the chest or on the opposite side. Stage IV means the cancer has spread to distant sites like the brain, bones, liver, or the other lung. Stage IV is further divided based on whether there is a single distant site or multiple ones.
The survival numbers reflect these stages clearly. According to the SEER database (covering 2016 to 2022), the five-year relative survival rate is 65.5% for localized disease, 38.2% for regional spread, and 10.5% for distant metastasis. These numbers have been improving, driven largely by better treatments and more people being diagnosed earlier.
How Lung Cancer Is Treated
Treatment depends on the type of lung cancer, its stage, the genetic profile of the tumor, and the patient’s overall health. For early-stage NSCLC, surgery to remove part or all of a lung is often the primary approach, sometimes followed by chemotherapy to reduce the chance of recurrence. Radiation therapy is another option, particularly for people who can’t undergo surgery.
For advanced NSCLC, treatment has been transformed by two developments: targeted therapy and immunotherapy. Targeted drugs work by blocking specific genetic mutations driving the cancer. If your tumor has an EGFR mutation or ALK rearrangement, for example, oral medications can often control the disease for months or years.
Immunotherapy works on a completely different principle. Lung cancer cells often produce a protein on their surface that acts like an “off switch” for the immune system’s T cells. When this protein locks onto T cells, it essentially tells them to stand down, allowing the cancer to grow unchecked. Immunotherapy drugs block this interaction, restoring the immune system’s ability to recognize and attack the cancer. These drugs can be used alone in patients whose tumors produce high levels of this protein, or in combination with chemotherapy. For many patients with advanced lung cancer, immunotherapy has become a standard part of first-line treatment.
SCLC is typically treated with a combination of chemotherapy and radiation. Because it tends to spread early, surgery is rarely an option. SCLC often responds well to initial treatment, but it has a high rate of recurrence, making it one of the more challenging forms to manage long-term.