Tumor markers for small cell lung cancer (SCLC) are measurable using blood tests, such as neuron-specific enolase (NSE). They can support the identification and management of cancer.

Doctors use a range of tests to measure different aspects of cancer and inform their clinical decisions. Tumor markers can inform doctors about the presence, severity, or possible treatment responses to cancer.

Keep reading to learn more about tumor markers for SCLC.

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Tumor markers are indicators that doctors use to gain information about the severity, location, or other factors relating to cancer in the body. They are typically proteins or other substances that cancer cells produce in larger quantities than healthy cells.

Doctors may take a range of different samples to measure these markers, including blood, urine, or stool samples. More recent approaches extract genetic information directly from the tumor, such as genetic mutations.

Tumor markers can provide information on a variety of factors that are helpful for:

  • screening, particularly in people in high-risk groups
  • differentiating cancer from a similar condition and diagnosing the condition
  • staging the severity of a cancer, such as measuring tumor markers in different tissues to determine how far the cancer has spread
  • determining a prognosis, such as measuring how aggressive the cancer might be
  • guiding treatment, such as examining genetic information for targeted therapies
  • assessing treatment responses, including monitoring effectiveness or identifying the recurrence of a tumor

Doctors will typically use tumor markers to supplement information from other diagnostic methods, such as a tissue biopsy.

For example, a doctor may test for information on NSE to diagnose and assess treatment response in people with SCLC. NSE is an enzyme that doctors can detect in the blood. It is a common tumor marker for people with SCLC and neuroblastoma.

While lung cancer is the second most common cancer in adults in the United States, only around 13% of cases are SCLC and 84% are non-small cell lung cancer (NSCLC). Less information is available on SCLC and there are fewer tumor markers specific to SCLC that doctors can use, relative to NSCLC.

Doctors might use various types of tumor markers for different purposes in people with SCLC. According to the National Cancer Institute (NCI), cytokeratin fragment 21-1 is a tumor marker relating to lung cancer in general.

A 2018 study found tumor markers that were useful for differentiating SCLC from NSCLC and noncancerous conditions include:

  • NSE
  • progastrin-releasing peptide (ProGRP)
  • carcinoembryonic antigen (CEA)

The researchers state that NSE is currently the most common tumor marker for identifying SCLC. This study suggests these additional markers could also support diagnosis and treatment decisions. Each of these markers is measurable using blood tests.

Immunohistochemistry is another tool that doctors use to diagnose diseases such as cancer, and can help them to differentiate different types of cancer. This method uses antibodies to check for specific tumor markers in a tissue sample.

For SCLC and carcinoid tumors, these markers are synaptophysin and chromogranin.

The normal ranges of tumor markers vary depending on the marker, type of cancer, and the individual.

The NCI reports that less than 2.5 nanograms per milliliter (ng/mL) is a normal range for CEA, but this can vary depending on the type of test. CEA up to 10 ng/mL can indicate severe disease and over 20 ng/mL suggests the cancer has spread.

The NCI does not give a specific threshold for NSE or ProGRP. It states that new tumor markers frequently become available which are not immediately included on its list. The NCI also has no formal guidelines for using tumor markers.

However, the 2018 study mentioned above found that values over 16.3 ng/mL and 66 picograms per milliliters (pg/mL) for NSE and ProGRP were useful in identifying SCLC.

Tumor markers provide useful information to doctors and healthcare professionals about the presence, severity, and other factors relevant for diagnosing and managing SCLC. However, doctors will use information from tumor markers in combination with other test results due to limitations that include:

  • Other health conditions can increase the levels of many tumor markers.
  • Some tumor markers can change in several types of cancer.
  • Some people will have cancer without clear changes in tumor markers.
  • Less common cancers have fewer tumor markers that are specific to that disease, such as SCLC.

Research is ongoing to identify more tumor markers and provide more specific information from existing tumor markers to doctors.

For example, there is a growing amount of research into the use of genetic information specific to certain types of cancer.

There are several methods doctors might use for measuring tumor markers, including:

Many tumor markers are measurable in the blood, including NSE, ProGRP, and CEA for SCLC. However, doctors will typically measure genetic tumor markers using biopsies directly from tumors.

Tumor markers provide useful information for identifying and managing cancer, including SCLC. Doctors will use tumor markers and information from various tests to inform clinical decisions, such as distinguishing a tumor from another condition.

There is currently a lack of clear evidence for tumor markers specific to SCLC. However, some tumor markers for SCLC could include NSE, ProGRP, and CEA. Research is ongoing to identify more tumor markers for SCLC and other cancers.