Cancer Related Neuropathy
Peripheral neuropathy is not uncommon in patients with cancer. It can result from the underlying cancer, poor nutritional status, paraneoplastic mechanisms, or neurotoxicity of drugs used to treat the tumor. Pre-existing neuropathy is also a risk factor for development of early or more severe chemotherapy induced neuropathy (Bruna et al, 2011).
Commonly used chemotherapeutic agents that can cause neuropathy include taxanes, vinca-alkaloids, platinum compounds, bortezomib, thalidomides, pyrimidine analogs, epothilones, alkylating agents, and topoisomerase inhibitors (Miltenburg and Boogerd, 2014).
Detecting the presence of neuropathy prior to initiating cancer treatment is important as it can result in the identification of a potentially treatable underlying cause, help decide on the selection of a less neurotoxic chemotherapeutic agent, and help exclude patients with pre-existing neuropathy from clinical trials of new chemotherapeutic drugs.
The typical presentation of sensorimotor neuropathy includes symptoms of numbness, pain, or muscle weakness, with sensory loss on neurological examination, and abnormal EMG and nerve conduction studies. However, the neuropathy can be asymptomatic and only recognized after suffering a cut or burn without feeling pain, or the neurological examination may be normal as is often the case in small fiber neuropathy (Lacomis, 2002). Electrodiagnostic studies are often not diagnostic in chemotherapy induced neuropathy, as they only measure the large, but not small nerve fibers, and are considered normal if the degree of axonal damage does not exceed the required diagnostic threshold.
Chemotherapy induced neuropathy is typically distal and axonal, with the nerve endings being the earliest affected (Han and Smith, 2013). These can best be assessed by punch skin biopsy, with determination of the Epidermal Nerve Fiber Density (ENFD). Several studies have reported that determination of the ENFD is more sensitive than electrodiagnostic testing in detecting chemotherapy induced peripheral neuropathy (Han and Smith, 2013). Chemotherapeutic agents also cause autonomic neuropathy, in which case the sudomotor fibers in skin can be assessed by determination of the Sweat Gland Nerve Fiber Density (SGNFD) (Giannoccaro et al, 2011).
Therapath is a specialty neuropathology laboratory that provides testing for Epidermal Nerve Fiber Density (ENFD) and Sweat Gland Nerve Fiber Density (SGNFD) for the diagnosis of small fiber neuropathy. The addition of these tests to the evaluation of oncological patients prior to deciding on treatment or inclusion in trials of new chemotherapeutic agents, or in those suspected of developing neuropathy while on treatment, would provide physicians with valuable tools to help prevent or care for their patients with cancer related neuropathies.