Welcome to HW, sorry you need to be talking to us.
Scary stuff for sure.
But, PSA isn't a test for cancer and the rate of change isn't a reliable predictor of cancer. BPH (enlarged), and infection are the more likely causes. Try to be very objective looking at this stuff. A jump from 14 to 18 simply indicates that a biopsy is likely a good next step (and yes, likely should have been done a year ago). It's the biopsy you need focus on - make sure he does it. You need the info from that.
and on the hopeful side, even if the worst is found, your father has plenty of treatment options that will keep the PC beast at bay for many, many years. It won't be fun and normal will change, but he'll be around for a long time.
Check out the stick threads at the top of the forum for a lot more good stuff.
Hang in there and keep us updated on progress,
I'll be in the shop.
Age 55, 52 at DX
PSA 4.2 10/11, 1.9 6/12, 1.2 12/12, 1.0 5/13, .6 11/13, .7 5/14, .5 10/14, .5 4/15
2 out of 14 cores positive
Treatment IGRT - 2/2012My latest blog post