>> brendan steele: no cancer.ncer. >> pelley: recurrent glioblastoma and now they tell you they cannot find it in your brain? >> brendan steele: yep. >> pelley: brendan steele has lived 35 months since his polio infusion. he's been cancer free for 19. dr. henry friedman, deputy director of duke's cancer center, has a theory about why the chemo worked this time, when it never had before. >> dr. henry friedman: shockingly, chemotherapy in patients who have previously failed it, once they've had the poliovirus therapy, now seem to have a new enhanced, almost extraordinary response to the chemotherapy as if the poliovirus has set up the tumor to be more responsive to chemotherapy. >> pelley: that was a surprise? >> friedman: that was a surprise. and for us to see this, it was a stunning observation, that is actually the platform for a future study that will involve chemotherapy and the poliovirus. >> pelley: the discovery changed their approach to nancy justice. you'll remember when we last saw nancy in march, 2015, d