Fifth Ovarian Cancer Consensus Conference of the Gynecologic Cancer InterGroup (GCIG): clinical trial design for rare ovarian tumours.

This manuscript reports the consensus statements on designing clinical trials in rare ovarian tumours reached at the fifth Ovarian Cancer Consensus Conference (OCCC) held in Tokyo, November 2015. Three important questions were identified concerning rare ovarian tumours (rare epithelial ovarian cancers (eOC), sex-cord stromal tumours (SCST) and germ cell tumours (GCT)): (i) What are the research and trial issues that are unique to rare ovarian tumours? There is a lack of randomised phase III data defining standards of care which makes it difficult to define control arms, but identifies unmet needs that merit investigation. Internationally agreed upon diagnostic criteria, expert pathological review and translational research are crucial. (ii) What should be investigated in rare eOC, GCT and SCST? Trials dedicated to each rare ovarian tumour should be encouraged. Nonetheless, where the question is relevant, rare eOC can be included in eOC trials but with rigorous stratification. Although there is emerging evidence suggesting that rare eOC have different molecular profiles, trials are needed to define new type-specific standards for each rare eOC (clear cell, low grade serous and mucinous). For GCTs, a priority is reducing toxicities from treatment while maintaining cure rates. Both a robust prognostic scoring system and more effective treatments for de novo poor prognosis and relapsed GCTs are needed. For SCSTs, validated prognostic markers as well as alternatives to the current standard of bleomycin/etoposide/cisplatin (BEP) should be identified. (iii) Are randomised trials feasible? Randomised controlled trials (RCT) should be feasible in any of the rare tumours through international collaboration. Ongoing trials have already demonstrated the feasibility of RCT in rare eOC and SCST. Mucinous OC may be considered for inclusion, stratified, into RCTs of non-gynaecological mucinous tumours, while RCTs in high risk or relapsed GCT may be carried out as a subset of male and/or paediatric germ cell studies.