While very provocative, the essay has several limitations. First, the cancer metaphor that Sontag describes was much more limited than she claims. While the psychosomatic movement may have conceived of cancer as an emotional failure, this view was never as widespread in Western culture as the romantic consumptive. I'm even skeptical about the latter. Second, Sontag never makes the second half of her case.
Serious illness is an important event in a life narrative.