Meggy, Sorry to hear about your news. I know how your husband feels. I too have metastatic colon cancer that has been in my lungs, a lymph node in my chest and my right adrenal gland and now is supposedly back in my lungs. I was first diagnosed 8 1/2 yeara ago.
First thing you should know is that a scan can't definitively diagnose cancer. A CT scan only sees differences in tissue density and a PET scan sees metabolic activity. Cancer tends to be denser and more active than normal tissue, but there are lots of other things that look the same. Half the healthy population given scans have spots on their livers and lungs that are not cancer. When I was first diagnosed I had a spot on my liver show up but it was not cancer. The only way to know for sure is to biopsy the spots.
As for the 5% chance of making it 5 years, that number is at least 10 years old as it is what I was told more than 5 years ago when my cancer was first found in my lungs and any number they givre us is atl least 5 yerars old. There has been a lot of good research over the past few years. I personally have had three drugs and tow surgeries that were not possible when I was first diagnosed. I have also hit the 5% end of the probability 5 times in a row so it is possible and he can do it.
From here he will likely first be givren more chemo with different drugs. There are several chemo drug regimines for colon cancer available so if one does not work then another will be tried. I have had most of them. There are also a lot of other treament options such as radiation, cyber knife, radio frequrency ablation and more. You two probably want to do soime research on them and be prepared to ask questions.
For second opinions you probably want to seek out Drs that are associated with a research hospital or clinic, preferabaly one tht has all of the different cancer sepcalities under one roof so that his cans can be reviewed by as large a team as possible.
If you need advice from a care giver you can look up my wife who goes by Queen Tatiana here on WhatNext. She has been wioth me for the entire journey and can give a caregiver's perspective.
Good Luck and let us know if you have more questions or anyother kind of help.