Prognostic value of tumour contour irregularity on surgical strategies for T1bN0M0 renal cell carcinoma: A multi-institutional study

•CID was significantly associated with WHO/ISUP grade III–IV.•CID was an independent prognostic factor of DFS in patients with T1b RCC.•PN was an independent prognostic factor of DFS in patients with high CID. To determine the prognostic value of tumour contour irregularity degree (CID) in surgical strategy options for T1bN0M0 renal cell carcinoma (RCC). We performed a retrospective multi-institutional review of 489 patients with T1bN0M0 RCC treated between January 2009 and June 2019. Cox regression and Kaplan-Meier analyses were performed to analyse the impact of CID on disease-free survival (DFS). The median follow-up time was 55 months (interquartile range, 40–81 months) for 55 (11.2 %) patients with metastasis or recurrence. Logistic analysis indicated that CID was associated with World Health Organization/International Society of Urological Pathology (WHO/ISUP) grades III–IV (odds ratio, 1.015; 95 % confidence interval [CI], 1.008–1.023; p