Having lost both his first wife Cassandra Harris and daughter Charlotte Brosnan to the disease, he called it "insidious."
He said, "To watch someone you love have his or her life eaten away bit by bit by this insidious disease, that part of your sorrow becomes an indelible part of your psyche. I held the generous, strong, beautiful hand of my first wife Cassie as ovarian cancer took her life much too soon. Just last year, I held the hand of my funny, wonderful daughter Charlotte before she, too, died from this wretched inherited disease."
Pierce also announced that Stand Up to Cancer will be putting together an ovarian cancer dream team.
Held at the Dolby Theatre in Los Angeles, Pierce was joined by celebrities including Jennifer Aniston, Halle Berry, Reese Witherspoon, Gwyneth Paltrow, Jon Hamm, Will Ferrell, Jesse Tyler Ferguson and more.
Ariana Grande was there to perform for her late grandfather who passed away from cancer. Lupe Fiasco, Common, Jennifer Hudson, Dave Matthews and The Who also performed.