“Platinum resistant” ovarian cancer: What is it, who to treat and how to measure benefit?

• Platinum resistant ovarian cancer is comprised of a heterogeneous and complex spectrum of diseases.
• Detailing time to progression, method of determining progression, histotype and genomic information may all improve interpretation of clinical trial results.
• More active agents and better methods of assessing benefit are needed.

“Platinum resistant” ovarian cancer was historically defined as disease recurrence within 6 months of completion of first-line platinum-based chemotherapy, although this is now more broadly applied to also include patients progressing within 6 months after multiple lines of chemotherapy. However, this definition ignores the heterogeneity and complexity of the spectrum of diseases that comprise “platinum resistant ovarian cancer” (PROC) and is innately flawed as it was initially derived using methods of detection of recurrence that would now be regarded as outdated. The outcome of patients with PROC is generally poor, with low response rates to further chemotherapy and a median survival of less than 12 months, but this is unpredictable and can be quite variable from study to study. This review outlines the complexity of PROC, examines how this impacts on the interpretation of the results of clinical trials, and explores how the definition may be improved. We also briefly describe the mechanisms of platinum resistance, the results of clinical trials to date as well as treatment options for patients with PROC and highlight the need for better methods of assessing clinical benefit in this poor prognostic sub group of patients.