It's possible a lack of sleep reduced his immune response to the cancer. The body has some natural cancer fighting mechanisms, and it's only the mutations that escape these that become malignant tumors.
It’s possible. But what’s more possible is spending the latter half of his life working on nuclear weapons and observing bomb tests took their toll.
It’s interesting how you guys are latching onto this man’s lack of sleep to speculate why he died young instead of the more obvious possibility, given his background.