"I feel powerful," says Ximena Gutierrez as she reaches the summit of Pico de Orizaba, Mexico's highest peak at over 5,600 meters. "I think that mountain climbing is more a form of therapy, rather than a sport," adds Ximena, who had her right leg amputated shortly before the age of 15 due to an aggressive form of bone cancer. The 22-year-old is one of a group of more than a dozen young French and Mexican cancer survivors and patients climbing Orizaba in freezing temperatures as part of the French-led charity 'Summits of Hope'.