NEW YORK — Joan Rivers' family is confirming that the comedian is on life support after going into cardiac arrest last week during a procedure at a doctor's office.Her daughter, Melissa Rivers, said in a statement Tuesday that her mother is on life support "at this time." Melissa said the family is extremely grateful for the public support.Joan Rivers was taken to Mount Sinai Hospital in Manhattan last Thursday. The 81-year-old comic and red carpet commentator has maintained a busy career as host of "Fashion Police" on the E! network and co-star of the WEtv reality show, "Joan & Melissa: Joan Knows Best?"Melissa Rivers said Tuesday that she knows that her mother would be overwhelmed by the continuing outpouring of kindness.