Tennis star Andre Agassi, saying that his family is his No. 1 priority, has withdrawn from the Sydney Olympic games, where he was planning to defend his gold title. Agassi, alluding to his revelation last week that his mother Elizabeth, 62, and his sister Tami, 31, both have breast cancer, said through a U.S. Tennis Association spokesman yesterday: "For personal reasons, as a consequence of a family medical situation, I will not be able to participate in the upcoming Sydney Olympics." Those games begin in little more than a week. No replacement was announced. According to sports writers, Agassi's vacated spot will likely be first offered to Wimbledon champ Pete Sampras and then Jan-Michael Gambill. Should they decline, Chris Woodruff is the likely candidate. As for the Agassi family, this week's new PEOPLE reports that in a show of support for his sister, who was losing her hair due to chemotherapy, brothers Andre and Phil shaved their heads. "For me," Tami told PEOPLE, "it was a good way to start this journey."