Treatment options for patients with ovarian cancer are moving beyond cytotoxic chemotherapy to novel hormones, immune interventions, and biologic agents. These innovative treatments offer the possibility of a non-toxic maintenance or consolidation therapy option for many patients after they have achieved their first or second remission. Although, consolidation therapy is a simple clinical concept that aims to prolong the interval of progression-free survival, the design of consolidation trials is challenging. We illustrate that a larger sample is needed for single-arm Phase-II consolidation trials depending on the duration of second line therapy (SLT), the time on the investigational therapy (IT) and the patient enrollment plan. A varying SLT and IT start time would compromise statistical power and comparability with historical data from other Phase II studies. We will discuss lessons learned from analyzing consolidation trials and offer guidelines in designing future consolidation trials, so that clinicians can decide when a single-arm study is promising and worthy of further study. Joint work with Howard Thaler, Paul Sabbatini and David Spriggs.