Introduction/Background*The Global Gynaecological Oncology Surgical Outcomes Collaborative aims to develop a network of gynaecological oncology surgeons, surgical departments and other interested parties that will have the long-term ability to collaborate on outcome studies. Presented is the protocol for the first collaborative study. Our primary objective is to evaluate international variation in thirty day post-operative morbidity and mortality following gynaecological oncology surgery between very high/high and medium/low human development index country settings.

Design International, multi-centre, prospective, observational, cohort-study. Two study-arms: very high/high and medium/low human development index (HDI) country settings. ClinicalTrials.gov registry: NCT04579861.

Inclusion criteria Women aged ≥18 years undergoing elective/emergency, curative/palliative surgery for primary/recurrent tubo-ovarian/peritoneal, endometrial, cervical, vulval, vaginal, gestational trophoblastic malignancies. Surgical modality may be open, minimal access (laparoscopic/robotic), or vaginal.

Exclusion criteria Non-gynaecological disease as the primary malignancy, diagnostic procedures, or any procedure not requiring a skin incision under general/regional anaesthesia.

Recruitment Patient data will be collected over a consecutive thirty day period through Gynaecological Oncology multidisciplinary teams and clinics across different HDI country groups. All data is collected on a customised, secure, password protected, central REDCap database.

Primary outcome Thirty day post-operative morbidity and mortality defined as per Clavien Dindo classification system.

Secondary outcomes Intra-operative morbidity/mortality; rate of tumour clearance; international prospective surgical outcomes database; comparison of current practice against selected tumour specific audit standards derived from the European Society of Gynaecological Oncology guidelines.

Sample size 1100 (550/arm) inflated by 20% to account for missing data and loss to follow up, at 90% power, α=0.05, will be able to determine a 10% point difference in thirty day post-operative morbidity and mortality following Gynaecological Oncology surgery between high/high and medium/low HDI country settings

Result(s)*GO SOAR1 is open to recruitment internationally.

Conclusion*The GO SOAR Collaborative aims to improve surgical outcomes through collaborative research. It will provide risk adjusted patient level outcome data collected via a centralised database to advise HDI country group specific policy formation.