Rapid and immediate loss of weight. This phenomenon has a different nature, unlike Anorexia Nervosa, does. In the case of the bone cancer, the patient is losing the weight unintentionally: the bones become lighter. Think about: are you experiencing a lot of stress? Have you changed your daily ration? Do you train a lot? If none of these is the right answer, it might be an alarming sign. People with bone cancer may quickly lose up to 10 pounds or more!