Mathematics probably hasn't invented a number high enough to count the theater people who have considered putting on solo shows about a loved one dying of cancer. Montana von Fliss, in her defense, waited six years after her father's death before she attempted Cancer: The Musical—so at least you know you're not about to endure the awful situation of watching someone trying to process grief onstage.
The first few minutes of Cancer put some other fears to rest: von Fliss poses as a "scientician" in a lab coat and glasses, fiddling with beakers and an overhead projector while trying to figure out the connection between matter and loss. (And though she employs the scientific method as a structure, von Fliss means both those words in their emotional senses—"matter" as in how much something matters to her, and "loss" as in the loss of her father.) She keeps things relatively light for the first third of the play, faux-sciencing her way through some exposition (her father was mentally ill and had a long history of substance abuse) and using some props and sight gags (confetti, stuffed cats, and a running joke involving rim shots for bad punch lines).
By the time von Fliss gets to the emotional core of the play, where she describes her father's death in vivid detail, she's sold the audience on her competence as a storyteller, despite some flaws. (At the performance I attended, von Fliss dropped several lines and seemed to lose her place on three occasions, which is not ideal, to say the least, for a one-person show.) She doesn't treat her audience like unwilling participants in a therapy session, so we go along for the ride—if you have issues with mucus, you should be alerted that you will be sitting in the middle of a chorus of gooey snuffles for the latter half of Cancer. At just about the point where you wonder if von Fliss is going to abandon her audience in a suck-hole of depression, she pulls out a celebratory musical conclusion that doesn't feel at all contrived. She's done her work, she's lived to tell the tale, and you'll be grateful that she did.