Vioxx was a long-term problem. Having that problem instead would be a great trade-off relative to untreated melanoma.
In actuality, even extremely aggressive therapies like high-dose chemotherapy with stem-cell transplant have shockingly low risk of death. Less than 5%. Bear in mind, that's for a therapy that literally wipes out all of your bone marrow. You know, the part of your body that produces your blood? Your body stops making blood and your immune system. And yet, we've gotten the death rate as low as it is.
And even if it did, it doesn't matter. You didn't read my comment at all. There are cancer treatments which can kill you outright, I know because I've received them. I think maybe you don't understand what cancer is. We can be very aggressive with the treatments. We have much, much bigger fish to fry than a small risk of myocarditis.