related to:
being connected or associated with something.
concerning:
means about a particular subject. The noun 'concern' indicates something that causes anxiety or unhappiness ,therefore many times 'concerning' is associated with negative happenings, but it is not a rule though. You could also say:
"He gathered the required information concerning the very details of the conference."
'with regard to'
means also concerning or relating to something.
This expressions or idiom is a bit formal though,so it won't be used that much in casual or informal speech, rather in formal writtings.
Since 'in regard with' is a bit formal , 'related to' and 'concerning' will be more often used.