Increase in paraneoplastic neurologic syndromes linked to greater awareness, testing

Increasing diagnoses of paraneoplastic neurologic syndromes in the U.S. correlates to heightened awareness by physicians as well as greater testing availability, according to a population-based epidemiology study published in Neurology: Neuroimmunology & Neuroinflammation.

“Paraneoplastic neurologic syndromes (PNSs) reflect immune responses (antibody or T cell mediated) against neural antigens expressed by an underlying, often unsuspected, tumor, which, when recognized early, are amenable to treatment with immunotherapy along with tumor treatment,” Shailee Shah, MD, department of neurology, Mayo Clinic, and colleagues wrote. “Epidemiologic data for PNS have been reported from Europe but are lacking for the United States, despite the growing recognition of these disorders and advances in test methodology.”

Researchers sought to ascertain all related factors, including associations with morbidity, leading to diagnosis of PNS in a sample of approximately 155,000 residents of Olmsted County, Minnesota, between Jan. 1, 1987, and Dec. 31, 2018. Participants were screened by scanning the medical records linkage system of the Rochester Epidemiology Project (REP) and determined by who met criteria for PNS as defined in 2004.

PNS incidence rates were calculated in three separate but overlapping time frames: 1987 to 2002, 2002 to 2018 and 1987 to 2018, using total number of person-years at risk per 100,000 person-years and adjusted by age and sex distribution consistent with the 2010 U.S. census.

All participants selected for the study were previously diagnosed with cancer. Patients diagnosed with dermatomyositis and myasthenia gravis with underlying tumors were included. Morbidity was estimated using a metric called “disability-adjusted life years,” a combination of years lived with a disability plus years of life lost while living with that disability.

Data showed 28 people (14 male, 14 female, mean age at time of diagnosis of 54.5 years old) were found to have PNS. Rate of PNS incidence in the population increased from 0.4/100,000 person-years (1987-2002) to 0.8/100,000 person-years (2003-2018). Statistical prevalence of PNS was found to be 5.4/100,000 people.

Researchers attributed the sharp rise of PNS incidence between the 1987 to 2002 and 2003 to 2018 periods to technological and medical advances that made it possible to recognize neural autoantibody markers, which aid in PNS diagnosis and bolstered disease classification. In addition, an increase in therapies to target cancerous tumors, such as immune checkpoint inhibitors used to treat small cell lung carcinoma, are likely a source from which to predict the frequency of PNS diagnoses.

“The rarity of PNS belies their significant mortality and morbidity burden and has important implications for resource allocation and health care planning,” Shah and colleagues wrote.

“Comparison of REP data to Minnesota and upper Midwest census data suggests that the results are generalizable to these regions and cautiously generalizable to the entire United States, which we suspect would be possible with our cohort due to the severe nature of PNS necessitating in-person evaluation by a neurologist and the increased local and national recognition of these disorders.”