Source : Webster's Revised Unabridged Dictionary (1913)

Egotistically \E`go*tis"tic*al*ly\, adv.
   With egotism.

Source : WordNet®

egotistically
     adv : in an egotistical manner; "he behaved egotistically" [syn: {selfishly}]
           [ant: {unselfishly}]