bob plefs is pruning his fruit trees. the cancer behind him. >> it's amazing that something can happen that quickly. a miracle. just a miracle. here i go, i thought i was going to die. i was preparing to die. now, i'm planning forward again. enjoying friends and family. >> so bob levis, like so many others in the penn trial, is back in the saddle, looking ahead to a healthier life, and no longer staring at the end of the road. >> correspondent chris bury tells us that bob levis has now been cancer-free for nine months and little emily whitehead she's been cancer-free for 20 months. >>> to get a better idea of what the treatment is involved, we turn to michel liguin. we appreciate you being with us. this is not a treatment for even every leukemia patient? >> not yet. this technology has focused so far on one particular target called cd 19. and so it is relevant to several luke keep yas, in particular the acute lymphoblastic leukemia in your piece. >> it has to be very serious before it is tried. it is relevant in your cent