Background We previously proposed two cfDNA-based scores (genome-wide z-score and nucleosome score) as candidate non-invasive biomarkers to further improve pre-surgical diagnosis of ovarian malignancy. We aimed to investigate the added value of these cfDNA-based scores to the predictors of the ADNEX model (Assessment of Different NEoplasias in the adnexa) to estimate the risk of ovarian malignancy.

Methods 526 patients with an adnexal mass scheduled for surgery were consecutively recruited in three oncology referral centers. cfDNA-based scores were calculated in pre-operative plasma samples. Logistic regression models were fitted for ADNEX predictors alone and after adding cfDNA scores. We reported likelihood ratio tests, the area under the Receiver Operating Characteristic curve (AUC), sensitivity, specificity, and Net Benefit for thresholds between 5% and 40%.

Results The study included 272 benign, 86 borderline, 36 stage I invasive, 113 stage II-IV invasive, and 19 secondary metastatic tumors. The likelihood ratio tests for adding the cfDNA variables to the ADNEX model were statistically significant (p<0.001 for ADNEX without CA125, p=0.001 for ADNEX with CA125). The accompanying increases in AUC were 0.013 and 0.003. Net Benefit, sensitivity and specificity were similar for all models. The increase in Net Benefit at the recommended 10% threshold estimated risk of malignancy was 0.0017 and 0.0020, respectively. According to these results, adding cfDNA markers required at least 453 patients per additional true positive.

Conclusion Although statistically significant, the addition of the cfDNA scores to the ADNEX model do not improve the ADNEX model in a clinically meaningful way.

TBo reports grants, personal fees, and travel support from Samsung Medison; travel support from Roche Diagnostics; and personal fees from GE Healthcare; all outside the submitted work. AC is a contracted researcher for Oncoinvent AS and Novocure and a consultant for Sotio a.s., Epics Therapeutics SA and Molecular Partners. BVC and DT report consultancy work done by KU Leuven to help implementing and testing the ADNEX model in ultrasound machines by Samsung Medison and GE Healthcare, outside the submitted work. TBa reports grants, personal fees, and travel support from Roche, Novartis, GSK, MSD, and AstraZeneca, all outside the submitted work. All other authors declare no competing interests.

The Trans-IOTA study is supported by the Research Foundation–Flanders (FWO) projects G049312N/G0B4716N/12F3114N, Internal Funds KU Leuven (project C24/15/037) and Kom Op Tegen Kanker (Stand up to Cancer), the Flemish cancer society (2016/10728/2603). DT is a senior clinical investigator of FWO (1803415N). TVG is a Senior Clinical Investigator of FWO (18B2921N). WF has a clinical postdoctoral mandate of the Foundation against Cancer (2023–031).

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Ethics committee of University Hospitals Leuven gave ethical approval for this work, as central Ethics Committee. Ethics committees of Università Cattolica del Sacro Cuore (Rome, Italy) and General Faculty Hospital of the Charles University (Prague, Czech Republic) gave ethical approval for this work.

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The pseudonymized data and data dictionary are stored in the KU Leuven Research Data Repository (RDR), https://doi.org/10.48804/TXL95Z. The dataset is not publicly available because this was not part of the informed consent. However, the dataset may be obtained following permission of prof. AC (an.coosemanskuleuven.be) and prof. DT (dirk.timmermanuzleuven.be) and after fulfilling all data transfer requirements.