<human>: Can you give me the gist of the text in a nutshell?

When we met she was dating someone, but I thought to myself, she and I would probably be a good fit.  
When she was free, I had someone I am seeing.  
(I prefer monogamy.)  
We're both single now and I'm pretty sure the attraction is mutual.  We've had some casual friendly dates and she has invited me to her home for dinner and a movie.  
The same day I accepted I got the diagnosis.  This is really new news for me.  
I prefer to be really upfront and not hide things.  I'm not even good about keeping my mouth shut about important stuff.  In this case, though, I'd prefer not to discuss until I know more.  I don't want her to be put off, by the thought that dating me is immediately turning serious ('by the way, you're signing on for this....') rather than the fun, I expect (and plan) for us to have together.  

So, my questions are:  
Do I have an ethical obligation to mention it, at least a little before we get physical or talk about seriously dating?
<bot>: Caught the (probably not going to kill me) cancer and a romantic invite together.  Feel weird about not telling, but don't want to mention it yet.