Can cancer cause ALS?

The link between cancer and ALS has been studied and debated for more than 50 years. The only established link is between malignant lymphoma (a type of cancer affecting the lymph nodes, spleen, and bone marrow) and a specific form of ALS. In very rare cases, the lymphoma can lead to the degeneration of motor neurons and trigger a paralytic disorder.

This condition is known as paraneoplastic motor neuron disease (or paraneoplastic ALS). “Paraneoplastic” can be translated as “beside (para) the tumor (neoplasm).” Paraneoplastic motor neuron disease differs from typical ALS in the presentation of its symptoms. Muscle wasting (myatrophy) in paraneoplastic ALS is severe, predominantly affects the trunk, and is largely symmetrical, whereas in typical ALS, muscle atrophy and weakness (even in advanced stages of the disease) are asymmetrical and show a preference for one side. Symptoms involving the upper motor neuron (increased reflexes or spasticity) are also absent or barely present in paraneoplastic ALS.

For other forms of cancer (particularly brain tumors, breast cancer, lung cancer, tumors of the gastrointestinal tract, skin cancer, and other solid tumors), no causal link to ALS has been established to date. Due to the prevalence of cancer in the general population, there are occasional cases of “concurrent disease” (known as “comorbidity”) involving cancer and ALS. Cancer treatment (including chemotherapy, radiation therapy, or bone marrow transplants) has not been shown to have a positive effect on ALS symptoms.