Small cell lung cancer (SCLC) is an aggressive form of lung cancer that has a short doubling time. The term “doubling time” refers to the amount of time it takes for a cell or tumor to double in size.

Compared to other types of lung cancer, SCLC grows rapidly and can quickly spread to other parts of the body.

This article provides information on the doubling time for SCLC. It also outlines the treatment options for different stages of the disease and explains different outlooks following treatment.

A doctor in his office holding up an X-ray of someone's chest as they look for small cell lung cancer.Share on Pinterest
Visoot Uthairam/Getty Images

Tumor doubling time is the amount of time it takes for a cell or tumor to double in size.

Doubling time is not the same for all cancers. Each cancer has its own doubling time, which is why some cancers are more aggressive than others. The shorter the doubling time, the faster it grows, and the more aggressive the cancer.

Different tumors of the same type of cancer can also have different doubling times.

Small cell lung cancer (SCLC) is an aggressive cancer that grows rapidly. A 2012 review notes that SCLC has a doubling time that can range anywhere from 25 to 217 days.

However, a 2021 review says that SCLC has a tendency to grow quickly, and it can have a doubling time as short as 25–30 days.

There are two stages to SCLC:

  • Limited-stage SCLC: The SCLC is confined to the chest area, which can mean the cancer has not spread:
    • beyond the lung it started in
    • to the space between the lungs
    • to one or more of the lymph nodes above the collarbone
  • Extensive-stage SCLC: The SCLC has spread beyond the borders specified for limited-stage SCLC. This means it could have spread:
    • widely throughout the lung
    • to the other lung
    • to the lymph nodes on the other side
    • to other parts of the body
    • to the fluid around the lung

Unfortunately, extensive-stage SCLC is present in two-thirds of people who are diagnosed with the condition. This is because many small cell lung cancers are aggressive and progress relatively quickly.

There is no specific timeline of progression from limited-stage to extensive-stage SCLC.

The best and most effective treatment for SCLC depends on the stage of the disease at the point of diagnosis.

Limited-stage cancers

The treatment for limited-stage SCLC may involve surgery, radiation therapy, chemotherapy, or some combination of these treatments.


A doctor may recommend surgical removal of the tumor and nearby lymph nodes if a person meets the following criteria:

  • the lung tumor is small in size
  • there are no signs of the cancer having spread
  • the person is otherwise healthy

Radiation therapy

Following surgery, a lab technician will inspect any lymph node biopsies for signs of cancer. If cancer is present, the doctor may recommend radiation therapy to the chest and collarbone. Radiation therapy may not be suitable for people with severe lung disease or other serious health issues.

Without preventative measures, SCLC can spread to the brain. This occurs in around half of all cases of SCLC.

In an effort to prevent this, a doctor may recommend a form of low-dose radiation therapy called prophylactic cranial irradiation (PCI).


In some cases, a doctor may also recommend chemotherapy to help kill any remaining cancer cells.

Combined chemotherapy and radiation therapy may produce more severe side effects than either therapy alone. However, combining the two treatments produces better results and improves the prognosis.

Extensive-stage cancers

For people who are otherwise healthy, the first-line treatment for extensive-stage SCLC involves chemotherapy, immunotherapy, and/or radiation. A doctor may choose one or multiple treatment options depending on a person’s cancer.

Combined chemotherapy and immunotherapy can help to shrink tumors, treat symptoms, and extend survival time.

If the initial round of treatment is successful, a doctor may offer radiation therapy to the chest. A doctor may also recommend radiation therapy in other areas of the body affected by the spread of cancer, which may include:

  • the brain
  • the spinal cord
  • the bones

Chemotherapy and radiation therapy may not be suitable for people who have poor overall health. In these cases, a doctor may prescribe either low-dose chemotherapy, palliative care, which uses treatments to alleviate pain and discomfort and improve quality of life, or both.

Small cell lung cancer generally has a poor prognosis. The median survival time for people who do not receive any treatment is 2–4 months.

With treatment, the overall 5-year survival rate for SCLC is 5–10%. In 2012, the overall 5-year survival rate for SCLC was 4–5%. These figures suggest that survival rates for SCLC are improving, but only slightly.

In addition, around 90% of people who receive treatment for SCLC relapse during the two years following therapy.

People with limited-stage SCLC have a better prognosis than those with extensive-stage SCLC. The 5-year survival rate for people with limited-stage is 30–35%, and most people lived 15–20 months.

In comparison, extensive-stage SCLC has a 5-year survival rate of 3%. The average survival time is about 7 months. Without treatment, this falls to 2–4 months.

Most SCLC relapses occur in the first two years after starting treatment. About 10% of people remain disease-free during that time.

Unfortunately, SCLC symptoms often do not develop until the cancer has progressed to other parts of the body. Consequently, doctors often diagnose SCLC in its later stages, when treatment is less likely to be effective.

A cancer diagnosis can be overwhelming, and a person may have many questions that they would like to ask their doctor. Having an open discussion with a doctor can help a person gain a better understanding of their condition and the treatment options available to them.

Some questions a person may want to ask their doctor include:

  • Is there any way to prevent or slow the progression of the cancer?
  • What is the best treatment option considering the current stage of the cancer and my overall health?
  • What is the goal of the treatment?
  • Are there any clinical trials I may be eligible to participate in?

SCLC is an aggressive lung cancer that has an exceptionally short doubling time. This means that SCLC tumors rapidly double in size and can quickly metastasize to other parts of the body.

There are two stages of SCLC: limited-stage and extensive-stage. Limited-stage disease is confined to the chest area, while extensive-stage disease has spread beyond the lungs and surrounding lymph nodes. For doctors, the stage of the disease is an important factor when considering a person’s treatment options.

The prognosis and overall survival rates for people with SCLC are relatively low. While limited-stage disease does offer better survival rates than extensive-stage disease, the prognosis is still poor. However, research into SCLC treatments is ongoing, and a person can ask their doctor if there are any clinical trials that they may be eligible to take part in.