Background: We completed a study evaluating a single intratumoral delivery of PVSRIPO in recurrent WHO grade IV MG patients (N Engl J Med. 2018 Jul 12;379(2):150-161). Some patients who originally benefitted from the infusion of PVSRIPO demonstrated tumor recurrence, and we hypothesized that retreatment could trigger an immune recall effect, further extending their survival. We now report the impact of second and third intratumoral reinfusion of PVSRIPO in patients treated in the original dose finding study. Methods: Eligible patients were adults with recurrent supratentorial WHO grade IV MG who were experiencing disease recurrence after having benefitted from the first infusion of PVSRIPO. Additional eligibility criteria included: solitary tumor 1-5.5cm in diameter; ≥4 weeks after chemotherapy, bevacizumab or study drug; adequate organ function; KPS≥70%; and positive anti-polio titer. One patient each was retreated at 1 x 10⁷ TCID50 and 1 x 10¹⁰ TCID50, and three patients were retreated on the identified phase 2 dose of 5 x 10⁷ TCID50. Results: As of 2/09/2019, five patients have received a second intratumoral dose of PVSRIPO on study, one of which received a total of 3 doses. The patients who received two infusions of PVSRIPO were retreated 72 months, 43 months, 34 months, and 6 months after the first infusion. One additional patient received a second infusion of PVSRIPO 60 months after the first infusion and a third infusion of PVSRIPO 78 months after the first infusion. All patients demonstrated soap bubble degeneration on imaging, and two patients demonstrated tumor contraction. No grade 3 or higher adverse events related to PVSRIPO were observed after retreatment. Three of these patients remain alive more than 81, 80 and 52 months following the first PVSRIPO infusion and more than 9, 20 and 18 months after the second infusion, respectively. Two patients died 63 months and 20 months after the first infusion of PVSRIPO and 19.6 and 14 months after the second, respectively. The patient treated 3 times received the third infusion more than 2 months ago. Conclusions: Intratumoral reinfusion of PVSRIPO via CED is safe, and encouraging efficacy results have been observed. Clinical trial information: NCT01491893