IBCN 2023: Long Term Recurrence Risk, Metastatic Potential, and Length of Surveillance of Low Grade Non-Muscle Invasive Bladder Cancer
This retrospective study analyzed 521 patients with primary TaLG diagnosed between 1989-2019 at a university center (Toronto, Canada). Risk of recurrence, progression to high grade Ta/T1, muscle invasion, metastases, and death due to BC at 5, 10, and 15 years were assessed. RNAseq analysis compared the transcriptomic profiles of 4 LG tumors that metastasized to non-progressing tumors. Inter-observer variability in pathological grade by expert pathologists was assessed in 80 cases.
The mean and median follow-up was 9.9 and 8.5 years, respectively. Among 521 patients (72.9% men, median age 67.0 years), 350(67.2%) recurred, 57(10.9%) progressed in stage, 20(3.8%) developed metastases and 15(2.9%) died from BC.
Of the patients recurrence-free for the first 5 years, 50 (50/251, 9.6%) developed BC within 20 years and 2 died of BC (2/521, 0.4%). Cancer specific survival was 99.1%, 97.8%, and 96.3% at 5, 10, and 15 years, respectively. Transcriptomic profiles between metastasized Ta LG and nonrecurring tumors were different, despite appearing phenotypically similar. Moderate concordance was observed using the 1973 WHO grading system (Kappa=0.41;95%CI=0.32-0.50), improved with the 2004 system (0.78; 95%CI=0.65-0.90).
These results challenge the assumption that LG Ta BC nearly never progress to potentially lethal disease, with 2.9% dying from BC. However, the risk of BC-related mortality is extremely low in patients recurrence-free for the first 5 years. Efforts are needed to minimize inter-observer variability in pathological grading as surprisingly even experts sometimes disagree between low and high grade.
Presented by: Amy Chan, Division of Urology, Department of Surgery, Mount Sinai Hospital, Sinai Health System, Toronto, ON, Canada
Written by: Stephen B. Williams, MD, MBA, MS @SWilliams_MD on Twitter during the International Bladder Cancer Network (IBCN) Annual Meeting, September 29-30, 2023, Montreal, Canada