Lung Cancer: Types, Differences, and Survival Rates

Lung cancer accounts for 12.4% of all cancers and is the most prevalent cancer worldwide. In the United States, lung cancer has the highest cancer-associated death rate. Although smoking is the leading cause, 10–20% of lung cancers occur in non-smokers.

There are two categories of lung cancer: small cell and non-small cell, which have subtypes within them. These cancer types are staged and treated very differently.

Understanding lung cancer

For both men and women, lung cancer is the second most prevalent cancer type. 20% of people diagnosed with lung cancer will die, making it the deadliest cancer. The average age of diagnosis is 70 years old. A person has a lifetime risk of 5–6% of developing lung cancer, which is higher in smokers than in non-smokers. The number of cancer cases is decreasing in the United States since 2006 by 1–3% per year due to fewer people smoking and more people quitting smoking.

Smoking causes about 90% of lung cancers. Lung cancer is more prevalent in males who smoke. Exposure to secondhand smoke increases a person’s risk of lung cancer by 20–30%. Environmental exposures to asbestos or radon, for example, can increase the risk of lung cancer, as can prior radiation for treatment of breast cancer and other cancers.

Types of lung cancer

There are two main types of lung cancer:

• Small cell lung cancer (SCLC).
• Non-small cell lung cancer (NSCLC).

SCLC comprises about 10–15% of all lung cancer cases, and NSCLC about 80–85%. SCLC has two major types: oat cell or small cell carcinoma and combined small cell carcinoma. NSCLC has three main subtypes: adenocarcinoma, large-cell carcinoma, and squamous-cell carcinoma.

Common signs and symptoms of SCLC and NSCLC

Signs and symptoms include:

Persons with lung cancer most often have the advanced disease stage when the symptoms appear. The most common symptom is an unexplained cough.

Diagnosing lung cancer

Lung cancer, whether SCLC or NSCLC, often presents with symptoms that lead to a chest x-ray or computed tomography (CT) scan of the chest. Sometimes, these tests happen for other reasons, and incidentally detect an abnormality that is concerning for a cancer. A doctor may order a positron emission scan (PET) to evaluate these imaging results further.

To confirm the cancer, a tissue biopsy is necessary. This is often via a bronchoscopy, or a procedure using a scope passed through the trachea to the lungs. Other methods of obtaining cancer cells include drawing off fluid from the lung when present in a procedure called a thoracentesis, or with a needle biopsy under CT guidance. A pathologist reviews the cells from the biopsy to reveal the type of lung cancer it is.

Once a lung cancer diagnosis is confirmed, more tests like blood work, a bone scan, or a magnetic resonance scan (MRI) of the brain are given consideration. A mediastinoscopy, or procedure to look at the lymph nodes in the chest may be necessary to evaluate for spread of the cancer outside of the lung. The lung cancer is staged when the results are available, to decide the next steps for treatment.

Staging and treatment of lung cancer

The staging of lung cancer is different for SCLC versus NSCLC. The treatments are also unique to the type and subtype of lung cancer. SCLC tends to spread rapidly. It is aggressive and often comes back. It is commonly treated with systemic therapy and radiation. NSCLC is initially treated with surgery if the person is healthy enough, the tumor is accessible, and it has not metastasized or spread outside of the lung and surrounding lymph nodes. There is a role for chemotherapy, radiation, immunotherapy, and targeted therapy depending on the stage and type of NSCLC.

SCLC: staging & treatment

SCLC has two stages:

• Limited-stage. Cancer remains in the lung or are localized in the lymph nodes up to the collarbone.
• Extensive-stage. Cancer has spread beyond the lung or lymph nodes.

SCLC tends to be highly responsive to chemotherapy and radiation therapy treatments. Surgery is reserved for limited-stage disease and is followed by additional treatment with chemotherapy and/or radiation. The brain is also often radiated to prevent SCLC from spreading there.

Extensive-stage SCLC has treatment options with chemotherapy, immunotherapy, and radiation, depending upon the age and health of the patient, locations of metastases, and other factors beyond the scope of this article.

NSCLC: staging & treatment

NSCLC staging most often follows the TNM staging system (where T stands for the size and extent of the main tumor, N - the spread to the nearby lymph nodes, and M - the spread to the distant sites or organs (metastasis). Based on this system the following stages can be determined:

• Stage 0. The tumors are known as in situ with very localized abnormal cells.
• Stage IA and IB. The tumors are up to 4 cm in size.
• Stage IIA. The tumors are 4–5 cm in size.
• Stage IIB. The tumors are 5 cm in size and do not spread to the lymph nodes, or are <4 cm in size and spread to lymph nodes in the lung.
• Stage IIIA, IIIB, IIIC. The tumors are of various sizes and have spread to lymph nodes in various locations in the chest.
• Stage IVA. The tumor has spread in the chest with one area outside of the chest or in one location outside of the chest.
• Stage IVB. The tumor has spread outside the chest in more than one place or organ.

Treatment for stage 0–I cancer involves surgery to remove the tumor, or if the patient is too weak to endure the operation, radiation to the cancer. A medical oncologist may also offer targeted cancer therapy. Treatment for stage II cancers is also surgery when possible, and if unable, radiation is considered. Chemotherapy, immunotherapy, and targeted therapy are potential options afterward.

In the case of stage III cancers, if the tumor can be removed without major complications for the patient, the first treatment is surgery. There are likely cancer cells left after surgery. Adjuvant treatment, or treatment after surgery, may consist of chemotherapy, radiation immunotherapy, and targeted therapies. These therapies are for stage III cancers that are unable to be surgically removed as well. Likewise, in stage IV cancers, these modalities are the mainstay of treatment.

Survival rates

For all lung cancers in the United States, the overall five-year survival rate is about 20%. This statistic is based on the stage of the cancer, the age and health of the patient, and type of lung cancer they have.

For SCLC, the five-year relative survival rate for women is 8% and for men is 6%.

For NSCLC, the five-year relative survival rate is higher in women (33%) than in men (23%).

In the last five years, there have been multiple new targeted therapies for lung cancer approved for use. Immunotherapy and targeted therapies have been game-changing, allowing people with lung cancer to live longer. In advanced cases, there are patients that have been cured with these therapies, which was unheard of prior to these new treatments. In cancer that is often deadly and discovered when advanced, the future holds promise.