Chromosomal instability is a hallmark of ovarian cancer. Here, we explore copy-number alteration (CNA) profiling in cell-free DNA as a potential biomarker to detect malignancy in patients presenting with an adnexal mass. We prospectively enrolled 68 patients with an adnexal mass, of which 57 were diagnosed with invasive or borderline carcinoma and 11 with benign disease. Cell-free DNA was extracted from plasma and analyzed by low-coverage whole-genome sequencing. Patterns of chromosomal instability were detectable in cell-free DNA using 44 healthy individuals as a reference. Profiles were representative of those observed in matching tumor tissue and contained CNAs enriched in two large datasets of high-grade serous ovarian cancer (HGSOC). Quantitative measures of chromosomal instability, referred to as genome-wide -scores, were significantly higher in patients with ovarian carcinoma than in healthy individuals or patients with benign disease. Cell-free DNA testing improved malignancy detection (AUC 0.89) over serum CA-125 (AUC 0.78) or the risk of malignancy index (RMI, AUC 0.81). AUC values of cell-free DNA testing even further increased for HGSOC patients specifically (AUC 0.94). At a specificity of 99.6%, a theoretical threshold required for ovarian cancer screening, sensitivity of cell-free DNA testing was 2- to 5-fold higher compared with CA-125 and RMI testing. This is the first study evaluating the potential of cell-free DNA for the diagnosis of primary ovarian cancer using chromosomal instability as a read-out. We present a promising method to increase specificity of presurgical prediction of malignancy in patients with adnexal masses. .

The adaptive immune system is involved in tumor establishment and aggressiveness. Tumors of the ovaries, an immune-privileged organ, spread via transceolomic routes and rarely to distant organs. This is contrary to tumors of non-immune privileged organs, which often disseminate hematogenously to distant organs. Epigenetics-based immune cell quantification allows direct comparison of the immune status in benign and malignant tissues and in blood. Here, we introduce the "cellular ratio of immune tolerance" (immunoCRIT) as defined by the ratio of regulatory T cells to total T lymphocytes. The immunoCRIT was analyzed on 273 benign tissue samples of colorectal, bronchial, renal and ovarian origin as well as in 808 samples from primary colorectal, bronchial, mammary and ovarian cancers. ImmunoCRIT is strongly increased in all cancerous tissues and gradually augmented strictly dependent on tumor aggressiveness. In peripheral blood of ovarian cancer patients, immunoCRIT incrementally increases from primary diagnosis to disease recurrence, at which distant metastases frequently occur. We postulate that non-pathological immunoCRIT values observed in peripheral blood of immune privileged ovarian tumor patients are sufficient to prevent hematogenous spread at primary diagnosis. Contrarily, non-immune privileged tumors establish high immunoCRIT in an immunological environment equivalent to the bloodstream and thus spread hematogenously to distant organs. In summary, our data suggest that the immunoCRIT is a powerful marker for tumor aggressiveness and disease dissemination.

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