"Four-day extracorporeal blood purification resulted in complete resolution of immune effector cell-associated neurotoxicity syndrome and greater than 95% reduction in interleukin-6 levels without side effects"
I mean yeah, its about balancing risks. I'm guessing that a ~2% chance of a cascade would mean that its not likley to be given as a first like of defence.
In a lot of cases we don't have other first line options. it may be no treatment die in 6 months, standard treatment die in 10 months, or this where 2% die in 1 month but 98% are cancer free 1 year later. All numbers above made up, but those are often what we are dealing with.
Of course where we have other cancer treatments that works well those should be a first line (at least for now - who knows how this will advance), but all too often we don't have good options.
