Postoperative Outcome of Cystic Renal Cell Carcinoma Defined on Preoperative Imaging: A Retrospective Study

Purpose We evaluated the postoperative outcome of cystic renal cell carcinoma defined on preoperative computerized tomography. We also sought to find the optimal cutoff of the cystic proportion in association with patient prognosis. Material and Methods In this institutional review board approved study with waiver of informed consent, 1,315 patients were enrolled who underwent surgery for a single renal cell carcinoma with preoperative computerized tomography. The cystic proportion of renal cell carcinoma was determined on computerized tomography. The optimal cutoff of the cystic proportion was explored regarding cancer specific survival. Renal cell carcinomas were categorized as cystic or noncystic renal cell carcinoma according to a conventional cutoff (ie cystic proportion 75% or greater) and an optimal cutoff. Postoperative outcomes were then compared between the 2 groups. Multivariate Cox regression analysis was performed to determine the independent predictor of cancer specific survival. Results Of the 1,315 lesions 107 (8.1%) were identified as cystic renal cell carcinoma according to a conventional cutoff. The postoperative outcome of cystic renal cell carcinoma was significantly better than that of noncystic renal cell carcinoma (p <0.001). Neither metastasis nor recurrence developed after surgery in patients with cystic renal cell carcinoma. In association with the cancer specific survival rate, the optimal cutoff of the cystic proportion was 45% and 197 cases (15.0%) were accordingly defined as cystic renal cell carcinoma. On Cox regression analysis, a cystic proportion of 45% or greater of the renal cell carcinoma was an independent predictor of a favorable outcome regarding cancer specific survival (HR 0.34, p = 0.03). Conclusions Cystic renal cell carcinoma defined on preoperative computerized tomography is associated with low metastatic potential and favorable outcomes after surgery. Particularly, a cystic proportion of 45% or greater is an independent prognostic factor for favorable survival.