Early Cancer Detection in Asymptomatic Subjects through Measurement of Crosslinked cf-Nucleosomes in Plasma

ABSTRACTO_ST_ABSPurposeC_ST_ABSPlasma cell-free nucleosome (cf-nucleosome) measurements are used in veterinary, but not human medicine, to identify asymptomatic subjects at high risk of cancer. Uniquely among plasma sandwich immunoassay tests, cf-nucleosomes are nucleoproteins with a complex electrochemistry. Formaldehyde crosslinking is common in the investigation of cellular nucleoproteins by chromatin immunoprecipitation. cf-nucleosome sandwich immunoassay similarly involves isolation from plasma by chromatin immunoprecipitation. We investigated immunoassay of crosslinked plasma cf-nucleosomes in human cancer samples. Experimental DesignPlasma cf-nucleosomes were covalently crosslinked by blood collection in tubes containing a formaldehyde-releasing agent. Plasma samples were collected from asymptomatic healthy volunteers, treatment-naive cancer patients diagnosed with one of 21 different cancer types, and hospitalized patients with non-cancer conditions. Samples were assayed for a variety of nucleosome species at two independent sites and using immunoassays available from different commercial manufacturers. The assay cutoff was set at the highest cf-nucleosome level measured for any asymptomatic control subject to obtain results for cancer patients at 100% observed specificity. ResultsAn elevated level of crosslinked plasma cf-nucleosomes was observed in 112 of 229 cancer patients tested (49% sensitivity), including 11 of 32 Stage I solid cancers (34% Stage I sensitivity). Elevated levels also occurred in hospitalized patients with non-cancer pathologies, but no false-positive results occurred among 150 asymptomatic control subjects. ConclusionsImmunoassay of crosslinked plasma cf-nucleosomes achieved clinically meaningful sensitivity for cancer at 100% observed specificity in asymptomatic subjects, and shows promise for the identification of asymptomatic individuals at high risk of an undetected cancer. SignificanceEarly detection of cancers by screening asymptomatic subjects through minimally invasive blood tests is a goal in oncology. We show that crosslinking of circulating cf-nucleosomes in human whole blood prior to immunoassay achieved clinically meaningful sensitivity for cancer (49% overall, 34% in Stage I disease) across multiple tumor types at 100% observed specificity among the asymptomatic controls tested, suggesting this technique may have broad utility for improving early cancer detection.