Carcinomatous meningitis (CM) can occur during late-stage cancer. It develops when cancer cells break away from the original tumor and invade the protective membranes that surround the brain and spinal cord.

CM is rare, accounting for about 4–15% of all solid tumor cancer cases. Although many types of cancer can cause this complication, cancers such as breast cancer, lung cancer, and melanoma are more likely to result in CM.

In this article, we discuss CM in detail, including its symptoms, causes, and outlook.

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CM is a complication of cancer. It occurs when cancer cells break away from the main tumor and invade the thin membranes that cover the brain and spinal cord, or meninges.

The name of the complication comes from two different medical conditions: carcinoma and meningitis.

Carcinoma is a type of cancer that begins in the epithelial cells. These cells line a person’s skin, organs, and internal passageways. According to the National Cancer Institute, carcinomas account for 80–90% of all cancer cases.

Meningitis is inflammation of the meninges. There are various causes of the condition, including a viral, bacterial, or fungal infection, parasites, and different cancer types.

CM can occur with most types of late stage cancer. The most common solid tumor cancer that experts associate with CM is metastatic breast cancer. The next most common form is lung cancer, followed by melanoma.

Although many types of cancer can lead to this complication, it is more likely to develop in certain cancers. These include:

Healthcare professionals may refer to CM using other names, such as:

  • neoplastic meningitis
  • meningeal metastasis
  • leptomeningeal carcinoma
  • leptomeningeal carcinomatosis
  • leptomeningeal metastasis
  • meningeal carcinomatosis

Symptoms of CM can vary, and they can affect the cerebrum, cranial nerves, and spinal cord.

A 2021 article reports that 2% of people with CM may have no symptoms at all.

The authors note that the most common symptom of CM is a headache, occurring in 39% of those with the condition.

The headache results from increased pressure in the skull or irritation of the meninges. If the cause is increased pressure in the skull, a person may also experience nausea that worsens in the morning.

The second most common symptom is confusion. It occurs due to the presence of active cancer cells in the cortex, which is the outermost layer of the brain. This can also lead to temporal lobe seizures, which can result in:

If CM affects the posterior fossa, which is the space in the skull near the brain stem, a person may experience:

If CM affects the spinal cord, initial symptoms include leg weakness and back pain or paralysis. Other symptoms can include:

  • segmental numbness
  • dysesthesia, which is unusual sensations, such as burning or prickling, in the legs or feet
  • pain
  • limb weakness

A person may experience bowel and bladder dysfunction if CM has affected the sacral nerve roots. The sacral roots are involved with the lower limbs and the area between the vaginal opening and anus.

CM develops as a complication of late stage cancer. It occurs when the cancer cells reach the cerebrospinal fluid, which surrounds the brain and spinal cord.

CM is a complication of several different solid tumor cancers and lymphoma or leukemia.

According to a 2018 study, of all CM cases:

  • 70% occur when a person is living with systemic cancer or cancer that has spread
  • 20% develop in people living with a stable cancer
  • 10% occur in people during their first manifestation of cancer

Some risk factors for developing CM include:

  • advanced cancer stages
  • parenchymal brain metastasis in people younger than 40 years
  • not receiving radiation following surgery
  • incomplete surgical removal, or resection, of brain metastasis

There is no known way to prevent CM from occurring in people living with cancer. However, an individual can take steps to lower their risk of cancer.

Some general tips to help reduce the likelihood of developing cancer, according to the Centers for Disease Control and Prevention (CDC), include:

Treating CM can be challenging. People with CM usually have late stage cancer that has spread to different parts of the body. This means that the outlook is often poor.

Treatment for CM tends to focus on:

  • improving neurological problems
  • managing CM symptoms
  • improving quality of life
  • prolonging survival

Medical professionals try to treat CM whilst minimizing toxicity.

A doctor will assess a person to decide which treatment options will be most suitable. They will evaluate the person’s tumor grade, the burden the condition is putting on their health, and their neurological status.

The doctor may also use the person’s Karnofsky Performance Status (KPS). This is a standard way of measuring how well someone with cancer can perform ordinary tasks.

The doctor can use a KPS to help determine the person’s prognosis, track changes in their ability to function, and determine their chances of survival.

Once they have carried out an assessment, they will work with the person to decide which treatment will be most appropriate.

Treatment options for CM include:

Radiation therapy

Radiation therapy uses X-ray beams to kill cancer cells. A healthcare professional will target the cells present in the meninges.

The authors of a 2021 article note that although radiation therapy can alleviate pain, it may not improve a person’s survival.

Intrathecal chemotherapy

Intrathecal chemotherapy involves injecting chemotherapy drugs into the intrathecal space. This is the space that holds the cerebrospinal fluid.

A healthcare professional will inject the chemotherapy drugs into the cerebrospinal fluid using a lumbar puncture or Ommaya catheter, which is a device doctors place beneath a person’s scalp.

Intrathecal chemotherapy is the main form of treatment, as it avoids the blood-brain barrier. This means that it can go directly into the area around the brain and spinal fluid, rather than being administered via the bloodstream.

A 2021 article notes that this form of treatment can extend a person’s survival.

Systemic chemotherapy

A doctor may use systemic chemotherapy to treat CM in individuals who are unable to undergo surgery, as it does not require the placement of the Ommaya catheter. Doctors may also combine it with other treatment regimens.

Systemic chemotherapy can improve a person’s survival and may be beneficial for various types of cancer, including breast and small-cell lung cancer.

Targeted therapy

This treatment targets the proteins that control how the cancer cells divide and grow. Examples include:

  • epidermal growth factor receptor tyrosine kinase inhibitors (TKI) to treat lung cancers with EGFR mutations
  • HER2 TKI to treat some breast cancers
  • BRAF to treat people with melanoma
  • anaplastic lymphoma KIs to treat some lung cancers

Other treatment options

Other treatments can include:

Diagnosis often starts with a physical examination and discussion about a person’s symptoms. Often, a person with a CM diagnosis is already living with advanced stage cancer and may also have other complications.

To diagnose the condition, a doctor may order an examination of the cerebrospinal fluid. They may also order an MRI of the brain, spinal cord, and other relevant areas.

However, it can be difficult to reach a diagnosis. This is due to the low sensitivity of diagnostic methods, which means it is possible for a doctor to misdiagnose the condition.

People with CM often have late stage cancer, which means that their outlook is poor.

The researchers behind a 2021 article note that without treatment, the average life expectancy for CM is 4–6 weeks. With treatment, this increases to 2–4 months.

People whose breast cancer has caused CM tend to have a better outlook and respond better to treatment. The average survival time of individuals with breast cancer and CM is 5–7 months.

It is of note, however, that although the outlook may be poor, some people survive for prolonged periods of time.

For instance, a 2016 study mentions a 65-year-old female who developed CM as a complication of breast cancer. After responding well to treatment, this study participant lived for another 9 years, passing away due to ischaemic bowel, which was unrelated to the cancer.

Anyone living with cancer who is experiencing new or worsening symptoms should consult a doctor.

The doctor can help with adjusting the treatment plan and planning for palliative care.

CM is a serious and often fatal complication of cancer. It occurs when cancer cells break away from the initial tumor and enter the meninges.

People living with late stage cancer, lung cancer, breast cancer, or some other solid tumor cancer are most at risk of developing the complication.

Diagnosing CM can be difficult, and treatment can extend a person’s life expectancy by several weeks.

A person should seek guidance from a doctor if they are living with or have survived cancer and are experiencing new or worsening symptoms that could result from CM.