The Whole of the Moon.

When Kirk, a top roller-blader, discovers that he has bone cancer in his leg, his pleasant affluent life is shattered. Even though amputation provides the best chance for survival; to him, losing skating means the end of life. His friends cannot cope with his condition, but his hospital isolation is relieved by Marty - a street kid survivor who was found dying of leukemia. Marty bullies, taunts, and challenges Kirk, until he begins to climb out of his depression. Marty seems afraid of nothing and, knowing she will die, wants to experience everything.