Although NfL levels were only modestly increased compared to controls in most patients, three of the adult cancer survivors had NfL values at least 25% above the institutional upper limit of normal using the same assay (<30 years: <380 pg/mL; 30 to <40 years: <560 pg/mL; 40 to <60 years: <890 pg/mL). Here, NEFL is linked to cancer.