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Small Cell Carcinoma (SCLC – Small Cell Lung Cancer)

Small Cell Carcinoma

Small cell carcinoma (SCLC or small cell lung cancer) is one of the rapidly spreading lung cancers. It was previously called Oat cell carcinoma.

SCLC (small cell lung cancer) differs from other types of lung cancers because:

  • It is a neuroendocrine cancer
  • It is the most aggressive form of lung cancer
  • It spreads rapidly to other parts of the body even in its early stages
  • It is highly sensitive to chemotherapy and radiation
  • It is frequently associated with systemic manifestations unrelated to the primary disease or paraneoplastic syndromes.
  • It is curable in its early stage, or limited stage, but incurable in the later stage or extensive stage.
Types of lung cancer sclc and non-sclc
Types of lung cancer

How fast does lung cancer spread without treatment? SCLC Vs non-SCLC

The metastatic potential or how fast cancer spreads depends on multiple factors. Generally, the following factors determine the metastatic potential of lung cancers:

  • The type of lung cancer (SCLC Vs Non-SCLC):

    • Small cell carcinoma spreads more rapidly than non-small cell lung cancers. By the time a person is diagnosed with SCLC, it has already spread in 70% of the patients.
    • Non-small cell lung carcinoma spreads slowly. It first spreads to local lung tissues and surrounding structures and then to distant parts.
    • By the time a person is diagnosed with non-small cell lung cancer, 55% of the patients already have distant metastasis.

Distant metastasis of lung cancer at the time of diagnosis

Small Cell Lung CancerNon-small cell lung cancer


  • Stage of lung cancer:

    • The stage of lung cancer is directly related to the metastatic spread of cancer. The higher the stage, the more likely cancer has spread to distant tissues of the body.
    • In fact, staging is usually done by the TNM system that includes Tumor size, Nodal spread, and Metastasis.
  • Location of the Cancer:

    • Lung cancers that are close to blood and lymphatic vessels spread rapidly to distant parts. In contrast, cancers that are isolated by non-viable tissue spread less rapidly.
  • Doubling time of cancers:

    • Certain cancers proliferate rapidly. The time for a cancer mass to double in size is called the doubling time. SCLC (small cell carcinoma) has a short doubling time. The cells proliferate rapidly and may double in size in less than a month.
    • Non-SCLC has a doubling time of about 50 to 130 days.

What is the most aggressive form of lung cancer?

SCLC (Small cell carcinoma) is considered the most aggressive type of lung cancer as it spreads rapidly to distant organs.

It is estimated that by the time a person is diagnosed with SCLC, 70 out of 100 people have already developed distant metastasis.

This could be because of the aggressive nature of cancer and fewer symptoms during the early stage when it could be curable.

Ways Through Which Cancer Spreads Rapidly

Cancer can spread through blood, lymphatics, and tissues:

  1. Lymphatic system:
    • The lymphatic system is where cancer spreads from its original site. The lymphatic vessels serve as cancer’s conduit to other body regions.
  2. Blood:
    • By entering the bloodstream, cancer spreads from the site of its initiation. Other bodily parts are reached by the malignancy via the blood arteries.
  3. Tissue:
    • Cancer grows into neighboring locations as it spreads from its original location.

Essential Info About SCLC (Small Cell Carcinoma):

Signs and symptoms of SCLC (Small cell carcinoma):

Signs and symptoms develop in most patients with SCLC (small cell carcinoma). 5% of the patients or even fewer than that may have no symptoms at the time of diagnosis.

In addition, most patients have a very short history. Patients may report symptoms developing only 8 to 12 weeks before they are diagnosed with small cell carcinoma.

Patients may develop cough and shortness of breath with occasional blood in the sputum. Fever and shortness of breath may occur when cancer involves the main bronchi resulting in their collapse and pneumonitis. People are usually wrongly treated as pneumonia at this stage.

Symptoms of Lung Cancer
Symptoms of lung cancer

When cancer spreads to the surrounding structures, signs, and symptoms may differ. For example:

  • Hoarseness of voice may occur if the lung involves the recurrent laryngeal nerve or the larynx
  • Facial swelling may occur when cancer obstructs the flow of major vessels (Superior vena cava syndrome.
  • Patients may report difficulty in swallowing if it involves the esophagus.
  • Stridor or noisy breathing may develop due to tracheal compression.

The signs and symptoms of small cell carcinoma may also be related to the organ involved once it metastasized. For example:

  • Cancer spreading to the brain may result in headaches, blurred vision, seizures, focal weakness, and loss of balance.
  • Small cell carcinoma that spreads to the bones may result in severe bony pains. Patients may develop fractures of the vertebra and long bones.
  • Metastasis to the liver can result in jaundice, nausea, vomiting, right upper abdominal pain, and itching.
  • Patients with adrenal involvement may develop hypotension, dizziness, and hyperpigmentation.

Symptoms may also arise as a result of paraneoplastic syndromes associated with small cell carcinoma. These symptoms may include:

  • Common paraneoplastic syndromes associated with SCLC (small cell carcinoma) are ACTH production at sites other than the hypothalamus, and ectopic ACTH production, endocrine, and neurological syndromes.
  • Patients may develop ataxia, imbalance, loss of peripheral sensations manifesting as numbness and tingling, and weakness.
  • Patients may become dark-skinned as a result of hyperpigmentation, and develop cushingoid features.
vaping EVALI (E-Vaping Associated Lung Injury)
Long-term effects of vaping

What are the different Types of SCLC (Small cell carcinoma)?

There are two main types of SCLC (small cell lung cancer):

  • Small cell carcinoma or oat cell carcinoma, and
  • Combined small cell carcinoma

These types are differentiated based on how they appear under the microscope, their metastatic potential, and how they respond to the treatment.

Biggest Risk Factor For Small Cell Carcinoma?

Risk factors include everything that raises your risk of contracting an illness. The presence of a risk factor does not guarantee the development of cancer just like the absence of a risk factor does not guarantee the absence of cancer.

If you might feel yourself being at risk of lung cancer, consult your doctor immediately.

smoking and lung cancer
Smoking and lung cancer

Tobacco smoking is the number one risk factor for small cell carcinoma. More than 95% of the patients who develop SCLC (small cell carcinoma) have a history of smoking.

Cigarette, pipe, or cigar smoking, either current smoking or in the past increase the risk of lung cancer. The risk of lung cancer increases with time spent smoking—the earlier in life one begins, the more frequently one smokes, and the longer one smokes.

These are some of the other risk factors for lung cancer:

  • Presence of active lung cancer or a past history of lung cancer in the family.
  • Exposure to asbestos, arsenic, chromium, beryllium, nickel, soot, or tar.
  • Residing in an area with air pollution.
  • Being exposed to passive smoking
  • Presence of a human immunodeficiency virus infection (HIV).
  • Absorbing radiation from any of the sources listed below:
    • Nuclear bomb radiation
    • Radiation treatment for the chest or breasts.
    • Imaging procedures like CT scans.
    • Radon at the workplace or home.

Treatment Options For Small Cell Lung Cancer

The following factors determine the prognosis and available treatments:

  • The stage of cancer, including whether it only affects the chest cavity or if it has spread to other parts of the body?
  • Age, sex, and overall well-being of the patient.
  • The prognosis for some patients also relies on whether they receive both radiation and chemotherapy.

Patients with SCLC might get a variety of treatments. There are six varieties of conventional treatment:

  • Chemotherapy
  • Laser treatment
  • Placing stents endoscopically
  • Radiation treatment
  • Surgery
  • Immunotherapy

Before, during, or after beginning their cancer treatment, patients might enroll in clinical studies. New therapies may be tried when a patient is enrolled in a clinical trial.

These trials may have some negative effects and before being registered in a clinical trial, further tests may also be required.

The treatment of SCLC depends on the stage of the disease.

hazards of smoking and vaping e cigarettes vaping health risks evali
Vaping health hazards

Staging of SCLC (small cell lung cancer):

SCLC has the following two stages.


By the time cancer has progressed to this stage, it has spread from the lung, the space between the lungs, or the lymph nodes on the top side of the clavicle to other parts of the body.


Cancer that is in this stage is still in the lungs where it first appeared and has not yet moved to the lymph nodes on the superior region of the collarbone or the space between the lungs.

Treatment of Limited-stage SCLC (small cell lung cancer):

Roughly one-third of the patients have limited-stage small cell carcinoma. Treatment of these patients is intended to completely cure them of the disease.

Limited-stage small cell lung cancer is treated with thoracic radiation and platinum-based treatment. In addition, patients may be given cranial radiation as a prophylactic measure to treat unidentified metastatic deposits in the brain.

Treatment of Extensive-Stage SCLC (small cell lung cancer):

The treatment of extensive stage small cell lung cancer is not effective in most patients and survival rates have not changed even with novel treatment strategies.

However, the recently FDA-approved humanized monoclonal anti-programmed death ligand 1 (PD-L1) antibody, Atezolizumab when combined with platinum-based chemotherapy, carboplatin, and etoposide has shown to improve survival rates.

Atezolizumab + Carboplatin + Etoposide is considered the first-line treatment of adult patients with extensive-stage SCLC (small cell carcinoma).

After treatment, recurrence is common. The chest, brain, or other parts of the body may encounter a recurrence of the malignancy.

hazards of smoking

Approved Chemo Drugs for SCLC (Small Cell Lung Cancer)

A list of the approved drugs for small cell lung cancer is presented here [Ref]

  • Afinitor (Everolimus)
  • Doxorubicin Hydrochloride
  • Durvalumab
  • Etopophos (Etoposide Phosphate)
  • Everolimus
  • Hycamtin (Topotecan Hydrochloride)
  • Imfinzi (Durvalumab)
  • Lurbinectedin
  • Methotrexate Sodium
  • Opdivo (Nivolumab)
  • Tecentriq (Atezolizumab)
  • Topotecan Hydrochloride
  • Trexall (Methotrexate Sodium)
  • Zepzelca (Lurbinectedin)

New Treatment for Small Cell Lung Cancer:

Novel biological medicines that are highly targeted drugs are being investigated in the treatment of lung cancer.

Although most of these investigational medicines have not been approved, they may change the course of illness and improve survival rates in patients with SCLC (small cell carcinoma).

A list of the biological medicines used in the treatment of small cell lung cancer is presented here:

  • Ceritinib (Zykadia)
  • Crizotinib (Xalkori)
  • Alectinib (Alecensa)
  • Brigatinib (Alunbrig)
  • Lorlatinib (Lorbrena)

Small Cell Lung Cancer Life Expectancy with Treatment:

Patients with extensive-stage small cell lung cancer have a treatment response rate of 20% or more. The median survival rate is about 7 months. Only 2% of the patients survive for 5 years or more.

Patients with limited-stage small cell lung cancer have a treatment response rate of about 80%. The median survival rate of patients with limited-stage small cell lung cancer is about 17 months. At 5 years 12 – 15% of the patients are alive.


Small cell carcinoma or SCLC is a highly aggressive form of lung cancer. It is usually diagnosed when the disease has already spread to distant parts of the body.

It has two stages, limited and extensive-stage. Limited-stage SCLC is curable if timely treated with novel effective drugs while extensive-stage SCLC has a very poor prognosis.

Patients may survive for 7 to 15 months depending on the stage of the disease.

vaping e cigarettes EVALI (E-Vaping Associated Lung Injury)
EVALI (E-Vaping Associated Lung Injury)

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Written by Dr. Ahmed

I am Dr. Ahmed (MBBS; FCPS Medicine), an Internist and a practicing physician. I am in the medical field for over fifteen years working in one of the busiest hospitals and writing medical posts for over 5 years.

I love my family, my profession, my blog, nature, hiking, and simple life. Read more about me, my family, and my qualifications

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