Possibilities of CT perfusion in renal tumor cryoablation: а retrospective study

Introduction: Modern surgical treatment of localized renal cell carcinoma (RCC) is focused on organ-preserving methods, including ablative technologies (radiofrequency ablation, microwave ablation, and cryoablation). Despite the safety of ablative methods, the risk of incomplete ablation and local recurrence of kidney tumors remains, necessitating effective tools for early diagnosis. Perfusion computed tomography (CTP) offers the possibility of quantitative assessment of microcirculation in the ablation zone and detection of preserved vascularization.

Objective: To analyze the potential of CTP for assessing the treatment effect of renal tumor cryoablation in the early and longterm postoperative periods.

Materials and methods: The study analyzed data from standard multiphase computed tomography (Std-CT) and CTP of 40 patients with renal cell carcinoma aged 36–76 years before, on days 5–7, and 3 months after cryoablation. Based on CT results, 37 patients were determined to have complete ablation of the tumor node, and 3 patients had incomplete ablation. Arterial flow (AF), blood volume (BV), and vascular wall permeability (CL) in the tumor area were assessed.

Results: In the group of patients with complete cryoablation (n=37), a statistically significant decrease in maximum CT density and perfusion parameters (BV, AF, CL) of the tumor was revealed on days 5–7 and 3 months after the procedure, reflecting ischemic changes and regression of tumor tissue. In patients with incomplete tumor ablation in the early postoperative period, areas of hyperperfusion in the cryodestruction zone were visualized, and a slight decrease in maximum densitometric values (HU) and perfusion parameters (BV, AF, CL) in the tumor node was noted. During follow-up at 3 months (n=2), an increase in density and a further rise in perfusion parameters in the residual tumor were detected, indicating preserved angiogenesis.

Discussion: The results of this study are consistent with the works of other authors and confirm that CTP can serve as an additional technique for monitoring after renal tumor cryoablation. A decrease in CTP parameters in the cryoablation zone indicated complete destruction of the tumor node, while an increase in CTP values in local areas of the postoperative region indicated the preservation of viable tumor cells and served as an indicator of their activity, which was expressed in the presence of residual tumor.

Conclusion: CT perfusion allows for assessing the treatment effect of cryoablation in the early postoperative period by evaluating changes in the quantitative characteristics of the microcirculatory bed in the solid component of the kidney tumor.

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