New Approaches for Immune Directed Treatment for Ovarian Cancer.

OPINION STATEMENT: The immune system plays an active role in the pathogenesis of ovarian cancer (OC), as well as in the mechanisms of disease progression and overall survival (OS). Immunotherapy in gynecological cancers could help to revert immunosuppression and lymphocyte depletion due to prior treatments. Current immunotherapies for ovarian cancer, like all cancer immunotherapy, are based on either stimulating the immune system or reverting immune suppression. Several approaches have been used, including therapeutic vaccines, monoclonal antibodies; checkpoint inhibitors and adoptive T cell transfer. Most of these therapies are still in early-phase testing (phase I and II) for ovarian cancer, but the initial data in ovarian cancer and successful use in other types of cancers suggests some of these approaches may ultimately prove useful for ovarian cancer as well. Ovarian cancer vaccines have shown only a modest benefit in ovarian cancer when used as monotherapy, but these agents may be able to enhance antitumor activity when combined with chemotherapy, checkpoint inhibitors, or other immunotherapies. Monoclonal antibodies have been explored in ovarian cancer but despite encouraging phase II data, randomized studies failed to demonstrate significant clinical benefit. Check point inhibitors have promising activity in several solid tumors and have demonstrated a favorable toxicity profile. Data from early clinical trials utilizing PD1 and PD-L1 inhibitors showed encouraging results. Ongoing clinical trials are evaluating the role of check point inhibitors in combination with chemotherapy. Adoptive T cell transfer involves the infusion of ex vivo activated and expanded tumor specific T cells, using various sources and types of T cells. While this approach has been explored in several hematologic malignancies, it constitutes early research in ovarian cancer. Immunotherapy remains investigational in ovarian cancer and the benefit of this approach in improving progression-free survival (PFS) or OS is unknown. Previous clinical trials have not selected patients based on biomarkers and this may explain the negative results. We expect to discover that tumor response will relate to the patient's immune features and specific tumor characteristics. We are only beginning to realize the potential of immunotherapy for ovarian cancer patients, and one goal of future clinical trials will be to identify subsets of patient based on histologic, molecular, and immune characteristics.