Defining Tumour Shape Irregularity for Preoperative Risk Stratification of Clinically Localised Renal Cell Carcinoma

Background: Unexpected adverse pathology is a major concern in surgical management of clinically localised renal cell carcinoma (RCC). Further studies are needed to improve preoperative risk stratification. Objective: To define and classify tumour shape irregularity (TSI) based on preoperative imaging, and to investigate its effect on pathological and oncological outcomes in clinically localised RCC. Design, setting, and participants: We retrospectively analysed 474 patients with cT1-2N0M0 RCC managed by partial or radical nephrectomy. Preoperative dynamic computed tomography was used to define and classify TSI, graded as 1 (completely elliptical shape), 2 (elliptical shape with minor and focal protrusions), or 3 (nonelliptical shape presenting with major and/or extensive protrusions). Intervention: Partial or radical nephrectomy. Outcome measurements and statistical analysis: A logistic regression analysis evaluated the risk factors for pT3a upstaging and Fuhrman grade 3–4. A Cox proportional hazard analysis assessed preoperative variables for recurrence-free survival (RFS). Results and limitations: The median tumour size was 3.5 cm, and 94 patients (20%) had (R)adius (tumour size as maximal diameter), (E)xophytic/endophytic properties of tumour, (N)earness of tumour deepest portion to collecting system or sinus, (A)nterior (a)/posterior (p) descriptor, and (L)ocation relative to polar lines (RENAL) score ≥10. TSI was graded as 1, 2, and 3 in 214 (45%), 151 (32%), and 109 (23%) patients, respectively. Higher TSI was significantly associated with a larger tumour size and a higher RENAL score. Overall, pT3a upstaging and Fuhrman grade 3–4 were observed in 45 (9.5%) and 116 patients (31% in 380 clear cell RCC cases), respectively. The incidence of pT3a upstaging and Fuhrman grade 3–4 was significantly higher in patients with higher TSI (0.5%, 8.6%, and 28% for pT3a upstaging and 12%, 33%, and 60% for Fuhrman grade 3–4 in TSI 1, 2, and 3 groups, respectively). In multivariable analyses, higher TSI was independently associated with adverse pathological outcomes. During the median follow-up of 6.0 yr, 49 patients (10%) developed recurrence. Multivariable analyses demonstrated that older age and higher TSI were independent risk factors for worse RFS. The limitations include the retrospective design. Conclusions: TSI may be a useful adjunct in preoperative risk stratification for adverse pathology and recurrence after surgery in clinically localised RCC. Patient summary: Tumour shape irregularity is significantly associated with unfavourable pathological outcomes, that is, locally advanced stage or high-grade cancer, and with a higher recurrence rate after surgery in patients with clinically localised renal cell carcinoma. Preoperative evaluation of the tumour shape may help in patient counselling and treatment decisions.