A search of the internet will reveal the five year survival rates for this general category of disease but it would tell you little about the specifics about what this particular person will face.
Lots of variables are in play as to prognosis of the person you know (I am assuming it is you for the remainder of the answer). Lots of things can enter the equation -- general physical health, specific type of cancer, other health conditions, treatment choices, stage of the disease, where it has spread to (if anywhere), treatment choices, age, nutrition, etc. And it is important to remember that even if the survival rates are low -- you could still be one of the survivors!
I would start by seeing a medical oncologist -- ideally one who tends to focus on your particular type of cancer. They will be in the best position to offer treatment alternatives and outlooks.
Think about what questions you want to answer and write them down before you go. Take someone with you -- task them with being sure all of your questions get asked and have them take notes. Don't hesitate to ask the doctor to slow down or provide more information. If you are interested in prognosis and treatment alternatives -- ask! Some patients seem to prefer less information in that area and some mds wait for the topic to be brought up.
An interesting article about this general topic is at at the New York Times Website under Health Care (registration required). It talks at length about the issue of hope and the sorts of concrete questions that you can ask.
Some patients fight the disease with everything medicine has to offer (some of which comes with significant side effects and/or contain invasive techniques). Other choose to receive no medical treatment. Still others pick and choose treatments with an eye towards quality of life rather than life extension. A lot of that is a reflection of the disease, your prognosis and, perhaps most important, your values.
Good questions to ask about any treatment approach (including no treatment)is for patients with my general characteristics: a) what is the impact on quality of life; b) what is the impact on life extension; and c) what are the potential side effects and how likely are they. If it doesn't work, what would want to try next? To what extent can you manage potential side effects?
Regardless of your philosophy, communicate your approach to your doctor. They are in the business of helping you and they can best meet your needs when they understand what they are.
Also, please remember that any decisions you make can be reversed -- you can start with very aggresive tx and back off if the disease responds poorly (or your body responds poorly to the tx). Finally, allow your oncologist to help you with all of the symptoms -- some come from the disease while others can come from the tx. Don't try and gut it out. Let your md know about things like depression, anxiety, pain, appetite, nausea. To some extent, these can be pretty effectively dealt with in the home.
While you still feel fairly well is also a good time to consider things like what heroic measures you would like taken if you fall very ill and fill out forms such a DPA for health care.
Good luck and best wishes.