My dad finally went to the doctor last week after a build up of symptoms. He's lost a considerable amount of weight, pain in his shoulder, cough that won't go away. They did a chest X-ray and his GP called to say that it looks likely that it is lung cancer but only after my dad pushed him for further information. Not an  deal way to be given this type of news. My dad is away on holiday this week and was told he's get a hospital referral for further investigation. Before he went away his voice was a little hoarse. Having spoken to him on the phone today, it sounds as though his voice has nearly gone. 
We have no idea, at this point, how far the possible cancer has progressed but I'm worried about the drastic change in his voice.