My Father Has Been Diagnosed With Cancer In His Omentum

My father has been diagnosed with cancer in his omentum ONLY for 18 months now. He has had 14 chemo sessions already and he has only become worse. What can we do? Should we look for another doctor or should we accept his faith? Doctors have told us chemo is the only option. He went from an average 6 foot 190 pound man to looking like he is 9 months pregnant. Help us please.