lems and cancer

Understanding the Overlap

Most people are aware that lung cancer can present with a range of symptoms. However, a lesser-known companion to this notorious disease, Lambert-Eaton Myasthenic Syndrome (LEMS), can be a tell-tale sign of its presence, particularly in cases of small-cell lung cancer (SCLC). In this article, we will explore the signs of lung cancer, discuss what LEMS is, what causes it, its signs and symptoms and the link between LEMS and cancer. We will also look at treatment options for LEMS, including Firdapse, which is used to treat LEMS in patients six years of age and older.

Signs of Lung Cancer

1. Persistent Cough

A cough that does not go away over time, or a change in a chronic cough, can be an early symptom.

2. Shortness of Breath

Breathing difficulties during normal activities can be a red flag.

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3. Chest Pain

Pain in the chest, shoulders or back that is unexplained and persistent can be a cause for concern.

4. Wheezing

A whistling or raspy sound when you breathe out can be due to lung cancer obstructing the airways.

5. Coughing up Blood

Also known as hemoptysis, coughing up blood can indicate advanced cancer.

6. Hoarseness

A change in voice or persistent hoarseness can signal cancer-impacting vocal cords.

7. Loss of Appetite

A significant drop in interest in food could be associated with cancer.

8. Unexplained Weight Loss

Losing weight without a change in diet or exercise can be a symptom of lung cancer.

9. Fatigue

Feeling unusually tired or weak without a clear cause is often reported in lung cancer patients.

10. Shoulder pain

In some instances, lung cancer can cause pain that extends to the shoulder area.

11. Swelling in the Face, Neck, Arms or Upper Chest

This can occur if the lung tumor presses against the superior vena cava, restricting blood flow.

12. Horner's Syndrome

Characterized by drooping or weakness of one eyelid, a small pupil in the same eye and possible reduced or absence of sweating on the same side of the face, is a rare condition that can be associated with lung cancer.

What Is Lambert-Eaton Myasthenic Syndrome?

LEMS is an autoimmune disorder characterized by weakness in the proximal muscles, such as those in the thighs and the upper limbs. It occurs when the immune system mistakenly targets the body itself, specifically attacking the voltage-gated calcium channels on the nerve endings. These channels are essential in triggering muscle contraction as they facilitate the release of acetylcholine, a neurotransmitter responsible for stimulating muscle fibers. When these channels are diminished, the muscle cannot contract properly, leading to weakness.

Symptoms of LEMS

Common signs of LEMS can include:

  • Muscle weakness that improves with activity.
  • Fatigue.
  • Trouble climbing stairs or lifting objects.
  • Dry mouth.
  • Erectile dysfunction in men.
  • Problems with automatic functions like blood pressure and heart rate.

LEMS and Small-Cell Lung Cancer

There is a notable link between LEMS and small-cell lung cancer. Roughly 60% of LEMS cases are associated with cancer, predominantly small-cell lung cancer (SCLC). This cancer-LEMS connection is so strong that some experts recommend that all patients diagnosed with LEMS be screened for SCLC.

SCLC is a type of neuroendocrine tumor that grows quickly and often starts in the lung’s breathing tubes. This association is due to a phenomenon called paraneoplastic syndrome, where an immune system response to a tumor inadvertently affects other parts of the body, such as the nervous system.

The immune system targets certain proteins produced by the tumor cells due to their similarity to proteins in the nervous system, leading to cross-reactivity and the symptoms of LEMS. Conversely, having LEMS can sometimes lead to an early diagnosis of SCLC because the onset of neurological symptoms prompts further investigation.

Treatment Options for LEMS

The management of Lambert-Eaton Myasthenic Syndrome revolves around treating its symptoms and, where present, the underlying malignancy. Here are some common therapy options.

  • Pyridostigmine: An oral medication used to treat symptoms of muscle weakness. It inhibits the breakdown of acetylcholine, allowing the neurotransmitter to remain active in the neuromuscular junction and improve muscle strength.
  • Firdapse: Firdapse (amifampridine) is approved specifically for the treatment of LEMS. It works by blocking potassium channels in the nerve cells, thereby prolonging the release of acetylcholine and improving muscle function.
  • Immunosuppressants: These can be prescribed to reduce the immune system's attack on the voltage-gated calcium channels. These include drugs such as prednisone, azathioprine and mycophenolate mofetil.
  • Plasma exchange: Plasmapheresis is a procedure that removes the patient's plasma and replaces it with fresh plasma or a plasma substitute, effectively removing the antibodies attacking the calcium channels.
  • Intravenous immunoglobulins (IVIG): Involves administering a mixture of antibodies to help block the harmful antibodies involved in LEMS.

Small-Cell Lung Cancer and Lambert-Eaton Myasthenic Syndrome

While LEMS is a rare syndrome, its strong association with SCLC highlights the importance of understanding both conditions. Recognizing the signs of lung cancer early, and acknowledging the neurological implications, like those seen in Lambert-Eaton Myasthenic Syndrome, not only provides insights into the underlying malignancies but also helps in devising a timely and effective treatment regimen, potentially improving patients' outcomes.