I don't know how slow or fast they grow but looking back I would say that my tumor was probably growing in the summer of 2012. I know this because of the signs I was having but didn't realize they were signs until after I was diagnosed in August of 2016. I had a very large tumor, so I am sure it was growing in 2012.
08/16/16 - TURBT - 1 tumor, T1HG, 7.5 cm x 7.5 cm x 1.8 cm, non-invasive papillary.
BCG treatments (15 rounds total - last March, 2018). As of latest cysto, Jun 19, 2019 - cancer free!