i agree with all the above advice. do you know what kind of Ca he had?
when you have another appt you might approach things from a more concern for him. he might open up to you so you could have an open conversation.

in the meantime (you're probably already doing this) get copies of the CD's and report for yourself. then you'll know what the results are before you go.

so, if you're honest with him about your concerns he might be honest in answering your Q's. but, come at him from a concerned point of view. i hope all this had made sense because it does in my head.