Writing anything as an expert is really poisonous to the writing process, because you lose the quality of discovery.
There's a phrase in Shakespeare: he refers to it as the 'hidden imposthume', and this idea of a hidden swelling is seminal to cancer. But even in more contemporary writing it's called 'the big C'.
Most discoveries even today are a combination of serendipity and of searching.
Robert Sandler is a child who died when he was three years old, and he is a child who was the first child that we know of to be treated with chemotherapy.
I had seen cancer at a more cellular level as a researcher. The first time I entered the cancer ward, my first instinct was to withdraw from what was going on - the complexity, the death. It was a very bleak time.
Why did I write 'The Emperor of All Maladies?' A 56-year-old woman with an abdominal sarcoma, having undergone two remissions and a relapse, asked me to describe what she was battling. By the time I had finished answering her, I realised that I had written 600 pages.