Defining progression in nonmuscle invasive bladder cancer: it is time for a new, standard definition

Purpose: Despite being one of the most important clinical outcomes in nonmuscle invasive bladder cancer, there is currently no standard definition of disease progression. Major clinical trials and meta-analyses have used varying definitions or have failed to define this end point altogether. A standard definition of nonmuscle invasive bladder cancer progression as determined by reproducible and reliable procedures is needed. We examine current definitions of nonmuscle invasive bladder cancer progression, and propose a new definition that will be more clinically useful in determining patient prognosis and comparing treatment options.

Materials and methods: The IBCG (International Bladder Cancer Group) analyzed published clinical trials and meta-analyses that examined nonmuscle invasive bladder cancer progression as of December 2012. The limitations of the definitions of progression used in these trials were considered, as were additional parameters associated with the advancement of nonmuscle invasive bladder cancer.

Results: The most commonly used definition of nonmuscle invasive bladder cancer progression is an increase in stage from nonmuscle invasive to muscle invasive disease. Although this definition is clinically important, it fails to include other important parameters of advancing disease such as progression to lamina propria invasion and increase in grade.

Conclusions: The IBCG proposes the definition of nonmuscle invasive bladder cancer progression as an increase in T stage from CIS or Ta to T1 (lamina propria invasion), development of T2 or greater or lymph node (N+) disease or distant metastasis (M1), or an increase in grade from low to high. Investigators should consider the use of this new definition to help standardize protocols and improve the reporting of progression.