Small-cell lung cancer is an aggressive type of lung cancer. It usually spreads to distant organs before it’s diagnosed. Tumors may double in size roughly every 1–7 months.

Small-cell lung cancer (SCLC) is one of the two main categories of lung cancer along with non-small lung cancer (NSCLC). SCLC is expected to make up about 10–15% of the approximate 238,340 cases of predicted lung cancers in the United States in 2023.

SCLC tends to be aggressive and spreads quickly. Despite improvements in treatment, about 70% of SCLC cases have already spread to distant organs when they’re diagnosed. SCLC commonly spreads to tissue such as:

  • the brain
  • bones
  • distant lymph nodes

The actual growth rate of SCLC can vary widely but is usually faster than NSCLC.

In this article, we look at how fast SCLC tends to grow and how its growth rate compares with NSCLC.

Small-cell lung cancer (SCLC) tends to be more aggressive than other types of lung cancer, such as NSCLC. SCLC has usually already spread to distant organs by the time it’s diagnosed.

Doctors most commonly divide SCLC into limited- and extensive-stage diseases.

When SCLC is contained to a small section of your lung that can be treated with one radiation field, it’s called “limited-stage disease.” When SCLC is spread widely throughout your lungs or distant tissues, it’s referred to as an “extensive-stage disease.”

With treatment, about 70–90% of people who have limited-stage disease and 50–60% of people with extensive-stage disease respond to initial treatment. Almost every person who has extensive-stage disease has a relapse within a year.

Doubling time

Doctors often use a parameter called “doubling time” to predict how fast a cancer grows. Doubling time is a measure of how long it takes for cancer to double in volume after it’s diagnosed. SCLC tends to have a fast doubling time compared with NSCLC.

The average doubling time of SCLC has been reported at about 86 days, and studies have reported a range in doubling time from 25–217 days.

For reference, in a 2020 study, researchers found that the doubling time of the most common type of NSCLC, adenocarcinoma, ranged from 278–872 days. The doubling time was more than 529 days in half of the 268 people in the study.

Mitotic count

Another way that doctors measure cancer growth is by its mitotic count. The mitotic count measures how many cells within a tissue sample are dividing. A higher miotic count means the cancer is growing more quickly.

The miotic rate of SCLC is usually very high at about 10 mitosis per 10 high power fields. This rate means that the person analyzing a tissue sample can see 10 cells dividing per 10 microscopic fields under the maximum amount of magnification, which is traditionally 400 times magnification.

About 70% of SCLCs have already spread to distant organs when the cancer is diagnosed. Common areas for it to spread are:

  • lymph nodes
  • brain
  • liver
  • bones
  • bone marrow
  • adrenal glands

Most cases of SCLC aren’t considered curable and have spread extensively at the time of diagnosis. Treatment for extensive-stage SCLC can potentially slow the progression of SCLC and increase your quality of life. For limited-stage SCLC, the goal is often to cure the cancer.

Most people with SCLC die within 2–4 months without treatment. With treatment, the average life span is now about 6–12 months for people with extensive-stage disease.

Standard treatment for extensive-stage disease includes:

  • Immunotherapy: Immunotherapy involves taking drugs that stimulate your immune system to attack the cancer.
  • Chemotherapy: Chemotherapy drugs contain chemicals that destroy cancer cells and other cells that replicate quickly.
  • Radiation therapy: Radiation therapy involves aiming high-energy waves at your cancer to destroy cells. For lung cancer, doctors usually perform external beam radiation in which they use a machine outside your body to administer radiation.
  • Prophylactic cranial irradiation: Prophylactic cranial irradiation involves administering radiation to your brain to prevent the future spread of cancer.

Doctors often report cancer survival statistics using 5-year relative survival rates. A 5-year relative survival rate measures how many people with a type of cancer are alive 5 years later compared with people without the cancer.

The 5-year Survival, Epidemiology, and End Results (SEER) relative survival rates for SCLC in the United States from 2012–2018 were as follows:

Stage5-year relative survival rate (%)
All SEER stages7

Learn more about the life expectancy of SCLC.

SCLC is an aggressive type of cancer that has usually spread beyond the lungs by the time it’s diagnosed. The overall outlook of SCLC remains poor despite improvements in treatment in recent years.

Doctors often use a doubling rate to measure how quickly cancer grows. The doubling rate of SCLC has been reported anywhere from 25–217 days.

The most common type of lung cancer, called “NSCLC,” tends to grow much slower.

A doctor can help you decide the best treatment for your cancer based on factors such as how far your cancer has spread, your overall health, and your personal preferences.