Blood test findings by Toronto doctors can detect cancerous tumour before it develops::Doctors at Princess Margaret Cancer Centre and The Hospital for Sick Children are helping detect cancer in some patients before a tumour develops or shows up on a medical scan.
Not discounting that logic, but it is also possible that the genetics of your partner get passed on for that gene instead of yours.
The part of the logic I’d struggle with is that if you only survive a few years after their birth, you’re creating an offspring that will loose their parent at a very young age and potentially putting your partner in a precarious position as a single parent. Not to mention the fact that every day you’ll look at your kid and think “I’ll never see them grow up, or graduate or get married or …” seems like a constant reminder of your upcoming doom.