<qa>  What is the effect of photopheresis on cancer cells?RATIONALE: Photopheresis allows patient white blood cells to be treated with ultraviolet UV light and drugs outside the body to inactivate T cells. Pentostatin may suppress the immune system and reduce the chance of developing graft-versus-host disease GVHD following bone marrow transplantation. Combining photopheresis with pentostatin and total-body irradiation may be effective in killing cancer cells before bone marrow transplantation. 