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1781. Three-Dimensional Topology-Based T-Index as an Indicator for Surgical Difficulty of Partial Nephrectomy in Patients with Small Renal Mass
Authors * Denotes Presenting Author
  1. Dongkyu An *; Severance Hospital, Research Institute of Radiological Science and (Center for Clinical Image Data Science), Yonsei University College of Medicine,
  2. Dae Chul Jung; Severance Hospital, Research Institute of Radiological Science and (Center for Clinical Image Data Science), Yonsei University College of Medicine,
  3. Jungwook Lee; Severance Hospital, Research Institute of Radiological Science and (Center for Clinical Image Data Science), Yonsei University College of Medicine,
  4. Seungsoo Lee; Yongin Severance Hospital, Yonsei University College of Medicine
Objective:
Our study aimed to suggest a new nephrometry score, the T-index, to describe the three-dimensional (3D) topology accurately by combining two surgically important anatomical factors: surface area of the kidney-tumor interface and distance from the tumor to the renal sinus. We evaluated the performance of the T-index as an indicator for partial nephrectomy (PN) surgical difficulty and its long-term complications.

Materials and Methods:
This retrospective, single-center study included 113 patients (80 men, 33 women; mean age, 53.3 years) who underwent PN for clear cell RCC (< 5.0 cm) between September 2007 and December 2014. Manual segmentation of the renal parenchyma, sinus, and tumor from each patient was done using preoperative CT images. T-index was calculated by adding up the reciprocals of the distances from all points on the tumor-parenchyma interface to the renal sinus. Correlations with perioperative parameters reflecting surgical difficulty and the impact of the T-index on chronic kidney disease (CKD) development were evaluated and compared with those of preexisting nephrometry systems.

Results:
The mean T-index among the 113 patients was 87.7 ± 60.1(1 mm). The T-index showed the strongest correlation with perioperative parameters compared to other nephrometry indices: total operation time (r = 0.261; p = 0.006), immediate postoperative creatinine difference (r = 0.427; p < 0.001), total length of hospital stay(r = 0.194; p = 0.042), warm ischemia time (r = 0.621; p = 0.011) and estimated blood loss (r = 0.243; p = 0.011). Among all patients, 89 patients did not experience complications throughout the 7-year follow-up period and 14 patients showed CKD development (stage 3). On univariable logistic regression, the T-index (odds ratio 1.01, 95% confidence interval 1.001–1.019) was one of the independent predictors of postoperative CKD developing with preoperative eGFR, age, Charlson Comorbidity Index, HTN and DM. The predictive model including the T-index and other presumed independent predictors showed equal performance compared with the predictive models based on other nephrometry indices. The areas under the curve were 0.873, 0.904, 0.884, 0.864, for the T-index, PADUA, RENAL and C-index, respectively.

Conclusion:
The T-index can be considered as a single value comprising key structural indicators for surgical complexity; the degree of intraparenchymal extension of the tumor and the distance between the tumor and renal sinus. Our findings suggest that the T-index can provide a quantitative and objective scoring system associated with surgical difficulty and long-term complications of PN. In conclusion, T-index is applicable nephrometry index to improve the preoperative radiologic evaluation and standardize surgical planning for PN in RCC patients.