Hi Paul, glad there is another runner here at last( in the nicest way) .
I run lots, in 2014 I did a couple of marathons and lots of smaller races, the big one was 100k non stop London to Brighton in 15 hours, fantastic.
In June 2014 I entered the Brighton marathion for April 2015 and "the wall" 110k race from Carlisle to Gateshead along Hadrians Wall. My best marathon time was my last 3 hours 47 age 49.
I was diagnosed Gleson 9 T4M1N1a October 2014. I have still run, I started chemo this week, however and that has been a bit of a game changer although I did 5 miles Friday. My head says that cycle week 1 don't run much just walk, week 2 do a bit and week 3 back to full running. I know that by the Brighton marathon I will be on week 14 of chemo and who knows what that will mean, as for the wall race we'll probably not gonna happen however........
My oncologist says he had never been asked the question about long distance running before but after much thought has told me I can run as much as I want as long as my body wants to ( a bit dangerous for me as mind over matter is how you get through marathons as the body always wants to stop!!) so that is what I will do, we have discussed diet which is now more vegetable less meat( in general) my only concern is dairy which I have reduced a lot but I am not sure if I am getting enough calcium for my bones although I am eating calcium rich veg. He agrees with you as do I, the fitter I am the better by body will fight it.
Like you I must have had PC for some time and like you my times were better last year although just before diagnosis I had a 5 min per hour reduction in speed. I live in Surrey so sorry we won't meet and reading what I have just written it's all me rather than you but I agree with your stance, listen to your body, eat all the right stuff and something I am rubbish at do the RICE but in full after every run, Rest, Ice, Compression, Elevation ie sit with your feet up, frozen peas strapped to your calves over some compression or dot flight socks, it really makes a difference in recovery. Today is a good day