Antitumor Effect of Nivolumab on Subsequent Chemotherapy for Platinum-Resistant Ovarian Cancer.

Platinum-resistant recurrent ovarian cancer is generally refractory to chemotherapy. Programmed cell death-1 (PD-1) signaling is a new target for antitumor therapy. The anti-PD-1 antibody nivolumab had a 10% durable complete response rate in our phase II clinical trial. However, how nivolumab affects sensitivity to subsequent chemotherapy remains unclear. We encountered several cases of unexpected antitumor response among patients who underwent palliative chemotherapy in the follow-up study of our phase II nivolumab trial (UMIN000005714). Several agents had an unexpected antitumor response in patients who were resistant or refractory to standard chemotherapeutic agents. In one patient, both pegylated liposomal doxorubicin (PLD) and nedaplatin (CDGP) resulted in partial response. In another patient, PLD and CDGP resulted in partial response and stable disease, respectively. These two patients remained alive on the cutoff date. These two cases raise the possibility that nivolumab might improve sensitivity to adequate chemotherapy for ovarian cancer.