Preoperative Plasma Cell-Free DNA Integrity Index in Clear Cell Renal Cell Carcinoma: An Exploratory Case-Control...

Evaluation of renal tumour masses relies on conventional imaging, which cannot reliably characterise the histopathological type, and no validated blood-based diagnostic marker is available for renal cell carcinoma. The cfDNA integrity index, the ratio of long to short circulating cell-free DNA (cfDNA) fragments, may reflect the necrotic origin of tumour-derived DNA and is a candidate qualitative marker of malignancy. This exploratory, single-centre case-control study assessed the preoperative plasma cfDNA integrity index in patients with clear cell renal cell carcinoma (ccRCC).

Plasma concentrations of 90 bp and 222 bp cfDNA fragments were measured by quantitative real-time PCR (qPCR) in 46 patients with histopathologically confirmed ccRCC (before surgery) and 17 healthy volunteers; the two groups were a convenience sample, were not matched, and differed in age and body-mass index. The cfDNA integrity index was defined as the ratio of the 222 bp to the 90 bp fragment concentration.

The cfDNA integrity index was higher in patients with ccRCC than in controls (median 0.28 vs. 0.15; p < 0.001, Mann-Whitney test) and rose progressively across healthy, non-metastatic (M0) and metastatic (M1) groups (p < 0.001, Kruskal-Wallis test; M0 vs. M1 p = 0.004). In unadjusted ROC analysis, both the integrity index (AUC 0.83, 95% CI 0.72-0.94) and its long 222 bp fragment component (AUC 0.93) discriminated patients with ccRCC from healthy volunteers, and the index separated metastatic from non-metastatic disease with an AUC of 0.79 (95% CI 0.64-0.88). The index was higher in high-grade (Fuhrman G3 + G4) tumours (p = 0.04) and in tumours with lymphovascular invasion (p < 0.001), and correlated with primary-tumour diameter.

In this exploratory cohort, the preoperative plasma cfDNA integrity index was higher in patients with ccRCC than in healthy volunteers and was associated with several adverse pathological features; these findings require confirmation in larger, matched studies that include benign renal masses before any diagnostic role can be claimed.