This is a Phase II trial will investigate if waiting until the time of chemical recurrence, denoted by rising CA125, to start a PARP inhibitor will lead to an improved time to next therapy with improved quality of life and at a lower financial toxicity.

PARP-I have shown efficacy as both monotherapy and as maintenance therapy. This trial will explore whether patients with recurrent ovarian cancer could derive the same efficacy benefit from a delayed start of a PARP-I compared to immediate maintenance therapy. Delayed start would have the benefit of sparing the physical, psychological, and financial toxicity associated with prolonged treatment. This approach would be particularly relevant in a population of platinum-sensitive patients who can have prolonged treatment-free intervals.

With widespread use of PARP-I, regardless of timing, understanding, and overcoming PARP-I resistance is becoming a major clinical need.

Enrollment will start within 8 weeks of completion of platinum-based treatment. Monitored with CA 125 levels every 28 days. Olaparib will be started when CA 125 rises by two-fold of their nadir value. Olaparib will be dosed at 300 mg orally twice a day, 28 days of treatment will be a cycle. Follow-up will consist of CA125 drawn every 28 days and CT scans obtained at doubling of CA- 125 and then every 12 weeks* to assess for recurrence or progression. Clinician- and patient-reported adverse events recorded every 28 days. Cancer-related worry and distress assessed every 28 days. Measures of quality of life and physical function, and financial toxicity assessed every 12 weeks.