[Jim W N]

“Lethality” - never seen that word before...

[Robert DeLong]

That's because you've lead a sheltered life I guess. 🙂 (Joking)

lethality
noun
1. Mortality.
2. The quality of being lethal; deadliness.

The lethality of cancer has decreased over the years.
The lethality of cancer still remains too high however.