Plasma DNA Methylation for Preoperative Classification of Renal Masses

Approximately 240 participants (acceptable range 200-250) will be enrolled before surgery. Plasma methylation testing will not guide clinical care and assay results will remain unavailable to treating clinicians and participants. The primary analysis compares pathologically confirmed renal cell carcinoma (RCC) with benign renal lesions. Non-RCC malignant renal lesions may be described separately. The final model is expected to contain 5-6 methylation markers. Model development, optimism correction, and cut-off stability will use at least 1,000 bootstrap resamples; the cohort will not be randomly divided into training and test sets. The marker combination, model coefficients or scoring algorithm, analytical quality-control rules, and positivity cut-off will be formally locked at study completion. This study is not an external validation study.

Primary outcomes

• Diagnostic performance of the final plasma DNA methylation classifier [At completion of enrollment and availability of final histopathology, anticipated within 3 months]]: Discrimination of the final plasma DNA methylation classifier for pathologically confirmed renal cell carcinoma versus benign renal lesions, assessed by the area under the receiver operating characteristic curve (AUROC) with a two-sided 95% confidence interval. Internal validation and correction for model optimism will be performed using at least 1,000 bootstrap resamples.

Secondary outcomes

• Sensitivity and specificity at the locked positivity threshold [At completion of classifier development, anticipated within 3 months]]: Sensitivity for RCC and specificity for benign renal lesions, each with two-sided 95% confidence intervals, at the final positivity threshold selected during classifier development. Threshold selection will prioritize an RCC sensitivity of approximately 90%, where technically achievable, while maximizing specificity among thresholds satisfying this sensitivity constraint.
• Additional diagnostic performance measures [[Time Frame: At completion of classifier development, anticipated within 3 months]]: Accuracy, positive predictive value, negative predictive value, positive likelihood ratio, and negative likelihood ratio for discrimination of RCC from benign renal lesions. Prevalence-dependent measures, including positive and negative predictive values, will be interpreted descriptively if enrichment of selected pathological categories is used.
• Diagnostic performance across pathological and tumor subgroups [[Time Frame: At completion of classifier development, anticipated within 3 months]]: Sensitivity summarized by major RCC histological subtype, pathological stage, grade, and tumor-size category; specificity summarized by major benign pathological category.
• Incremental performance beyond routine clinical and imaging variables [At completion of classifier development, anticipated within 3 months]]: Change in discrimination and exploratory decision-curve analysis when the methylation score is added to prespecified clinical and radiological variables.

Sex: All, ages: 18 Years to any

Inclusion Criteria:1.Age 18 years or older. 2.A renal mass identified by computed tomography and/or magnetic resonance imaging.

3.Partial nephrectomy or radical nephrectomy planned as part of routine clinical care.

4.Preoperative peripheral blood collection feasible before surgery or other treatment of the index lesion.

5.Final postoperative histopathological diagnosis expected to be available. 6.Written informed consent provided.

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Exclusion Criteria:7.Systemic anticancer therapy, radiotherapy, local ablation, or surgery/pathological sampling of the index renal lesion before study blood collection.

8.Concurrent active malignancy requiring systemic treatment that, in the investigator's judgment, could materially interfere with interpretation of the methylation assay.

9.Severe acute infection or another uncontrolled systemic condition that could compromise biospecimen quality or study procedures.

10.Inadequate preoperative blood specimen or failure of prespecified analytical quality-control requirements.

11.No definitive pathological diagnosis of the index renal lesion. Any condition that, in the investigator's judgment, makes participation inappropriate.

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