I actually had someone reference this to me recently and checked at a local bookstore for it. I had not heard of it, but was intrigued. This is an article John Piper wrote in 2006 after being diagnosed with cancer himself. Here are the main points:
1. You will waste your cancer if you do not believe it is designed for you by God.
2. You will waste your cancer if you believe it is a curse and not a gift.
3. You will waste your cancer if you seek comfort from your odds rather than from God.
4. You will waste your cancer if you refuse to think about death.
5. You will waste your cancer if you think that “beating” cancer means staying alive rather than cherishing Christ.
6. You will waste your cancer if you spend too much time reading about cancer and not enough time reading about God.
7. You will waste your cancer if you let it drive you into solitude instead of deepen your relationships with manifest affection.
8. You will waste your cancer if you grieve as those who have no hope.
9. You will waste your cancer if you treat sin as casually as before.
10. You will waste your cancer if you fail to use it as a means of witness to the truth and glory of Christ.