A treatment that helps the human body fight blood cancer is showing early signs of promise against some solid tumors. The treatment strengthens the person’s natural defenses against disease. Its success against tumors suggests this method might be extended to more common cancers in the future. The treatment is called CAR-T therapy. It involves making genetic changes to some of a patient’s own cells to help them recognize and attack cancer. Richard Carlstrand of Long Key, Florida, had the therapy more than a year ago for mesothelioma, a cancer of the lining of the lungs. “We were going into unknown territories” to try this, he told The Associated Press. But now he shows no sign of cancer and “I couldn’t be happier,” Carlstrand said. Experts discussed results of his and other cases at an American Association for Cancer Research conference last month in Atlanta, Georgia.