Prostate removal not complete..

I had me prostate removed on 28th August this year as i was told I had 2 localised cancer growths on my prostate.

The MRI imaging showed it to be wholly internal to the prostate and no further spread was evident.

On having my 8 week review with the consultant, he informed me that the cancel was not wholly contained withing the prostate and it had in fact broken out of the shell of the prostate.and as such I will still have cancel cells within me.

I was shocked by this news as I went in to the appointment believing I was going to get the all clear, but now I am in limbo.

I am to be monitored every 2 months for PSA markers and if they show a rise, then action will be taken.

But what I now want to know after having had time to digest the information is...

1: why is radio therapy / chemo therapy not an option to kill the cells that are left?

2: Am I just waiting for the cells to attach somewhere/anywhere else in my body and start multiplying again?

3: is this a common outcome from radical prostatectomy?

4: is there a % figure we can assign to the likely-hood of getting further cancer now?

5: should I be worried?

Any thoughts/comment greatly received.

Thanks

Martin