Neo-adjuvant Pembrolizumab in Primary Stage IV Ovarian Cancer

Long-term survival in stage IV serous ovarian, peritoneal, and fallopian tube cancer is poor and has not significantly improved over the last decades. Standard treatment consists of debulking surgery and six courses of carboplatin and paclitaxel. Nevertheless, the disease recurs in \>90% of women, usually within two years. Since early observations that the presence of infiltrating T cells is associated with improved outcome, ovarian cancer is linked to a potential benefit of immunotherapy.10 More recently, T cell checkpoint blockade with anti-PD1 and anti-PDL1 have shown promising activity in platinum resistant ovarian cancer with objective and durable responses in 10-20% of patients. This finding raises the question whether anti-PD1 could also play a role in first line treatment of ovarian cancer. To fully use the power of T cell checkpoint inhibition, sufficient TCR stimulation is required. Importantly, the amount of antigen that can provide this signal will correlate with tumor load, and because of this adjuvant immunotherapy may work most efficiently, when initiated prior to surgery. In addition, we postulate that antigen retrieval will increase after induction treatment with cytotoxic therapy. To address these questions, we propose a feasibility study in patients with FIGO stage IV serous ovarian, peritoneal, or fallopian tube cancer in which we evaluate pembrolizumab added to standard treatment for its capacity to induce and broaden T cell responses against neo-antigens.