Immunotherapy for paraneoplastic neurological disorders

The Utility of FDG-PET/CT in Clinically Suspected Paraneoplastic Neurological Syndrome: A Literature Review and Retrospective Case Series

Paraneoplastic neurological syndrome (PNS) describes a spectrum of rare, heterogeneous neurological conditions associated with an underlying malignancy. Diagnosis of PNS is inherently difficult, with frequent misdiagnosis and delay. The literature suggests an underlying immune-mediated pathophysiology, and patients are usually tested for the presence of onconeural antibodies. With direct tumor therapy being the most effective method of stabilizing patients, there is a strong emphasis on detecting underlying tumors. The sensitivity of conventional CT imaging is often inadequate in such patients. While FDG-PET imaging has already been shown to be effective at detecting these tumors, FDG-PET/CT, combining both structural and functional imaging in a single study, is a more recent technique. To study the utility of FDG-PET/CT, we conducted a systematic literature review and a retrospective study. We identified 41 patients who underwent imaging for clinically suspected PNS at the regional PET-CT and neurosciences center based at the Royal Preston Hospital between 2007 and 2014 and compared the results to conventional investigations. Five patients had FDG-PET/CT tracer avidity suspicious of malignant disease, and four of these were subsequently diagnosed with cancer. Sensitivity and specificity were calculated to be 100 and 97.3%, respectively, with positive predictive value 80% and negative predictive value 100%. This compares to a sensitivity and specificity of 50 and 100%, respectively, for CT and 50 and 89%, respectively, for onconeural antibodies. These findings are in line with previous studies and support the diagnostic accuracy of FDG-PET/CT for the detection of underlying malignancy.

Paraneoplastic syndromes affecting the nervous system

The paraneoplastic neurologic disorders (PND) are a diverse group of diseases characterized by the presence of neurologic dysfunction in the setting of a remote cancer. PND can affect almost any part of the nervous system, and are most commonly associated with lung cancer (small cell) and gynecologic tumors. Laboratory studies have demonstrated that an autoimmune response links the neurologic disorder and the cancer, and established a model whereby the cancer is believed to initiate the syndrome by expressing a protein antigen normally expressed in the nervous system, leading to anti-tumor immune response followed by autoimmune neurologic symptoms. We review the currently known PND and their pathogenesis.