Luyckx 2012.

Study characteristics
Methods	Retrospective review of medical records of patients treated in 7 French gynaecological oncology and surgery centres.
Participants	Women with FIGO stage IIIC and IV (pleural invasion only) ovarian, tubal or peritoneal epithelial carcinoma who underwent either primary or interval debulking. All had ≥ 6 cycles of carboplatin plus paclitaxel (enrolment 1 January 2003 to 31 December 2007) Age: median 59 years; range 24–90 years FIGO stage IIIC: 441 (83.7%); IV: 86 (16.3%) Tumour cell type: serous papillary 382 (72.8%), mucinous: 11 (2.1%), endometrioid: 54 (10.3%), clear cell: 13 (2.5%), undifferentiated 54 (10.3%), other: 11 (2.1%) Tumour grade 1: 34 (8.3%), 2: 138 (33.8%), 3: 236 (57.8%), unknown: 119 Ascites: median 50 mL; range 0–8000 mL Residual disease: no gross visible: 374 (71.1%), 0–1 cm: 97 (18.5%), > 1 cm: 55 (10.5%) Peritoneal cancer index: median 10.0 Upper abdominal lesion: 0 mm: 175 (38.5%); 0–25 mm: 182 (40.0%); > 25 mm: 97 (21.4%) Baseline details not presented according to type of surgery.
Interventions	Intervention 1: ultra‐radical surgery involving a combination of digestive tract resections (right colon and caecum, total colectomy, and others), organ resection (spleen, gallbladder, partial gastrectomy, and others), coeliac lymph node dissection, and total abdominal peritoneum stripping in addition to standard surgery (group 2B in the study). Intervention 2: standard surgery plus relatively routine upper abdominal surgery (group 2A in the study). Comparison: standard surgery with hysterectomy, bilateral salpingo‐oophorectomy, rectosigmoid resection, infragastric omentectomy, pelvic and aortic lymphadenectomy, and, when applicable, appendectomy (group 1 in the study).
Outcomes	Overall survival, disease‐free survival
Notes	Follow‐up: median 49 months Retrospective non‐randomised study. We assume that the decision to perform simple or radical procedures was determined by the surgeon. Confounding by indication could not be excluded. Participant and disease characteristics not reported per type of surgery. Blinding not reported (but may not be relevant to this research question). Sample also included a mixture of primary and interval debulking surgery. Adjusted HRs were derived from a prognostic model. Characteristics were selected based on statistical significance in the univariate analysis (P < 0.10) and not on including putative confounders in the analysis, irrespective of statistical significance.
Risk of bias
Bias	Authors' judgement	Support for judgement
1. Bias due to confounding (a–d)	High risk	Domain had a critical risk of bias: no known prognostic factors that have potential for confounding of the effect on intervention. Information collected retrospectively.
2. Selection bias (a)	Low risk	Intervention and follow‐up start were simultaneous as a rule for cytoreductive surgery. No evidence of selection into the study due to variables measured after the intervention since participants were included retrospectively.
3. Classification of interventions (a–b)	Low risk	Well‐defined surgical interventions based on type of surgical procedure: group 1: standard surgery; group 2A: standard surgery plus relatively routine upper abdominal surgery; group 2B: ultra‐radical surgery
4. Deviation from intended interventions (a–c)	Unclear risk	No evidence of any deviations from interventions or usual practice but may be due to omission or that deviations did not happen.
5. Bias due to missing data (a–b)	High risk	Domain had a moderate‐to‐high risk of bias: all selected participants may have been included in the analyses but this could not be confirmed. Therefore, it was sensible to judge the missing data domain as being at moderate‐to‐high risk of bias.
6. Measurement of outcomes (a–b)	High risk	Domain had a critical risk of bias: adjusted HRs are derived from a prognostic model based on univariate significance testing (P < 0.10) and not on including putative confounders in the analysis, irrespective of statistical significance. Also, adjustment were made for residual disease and this was likely to distort the estimate of survival as this adjustment was made after surgery and was a key prognostic factor.
7. Reporting bias (a–c)	Unclear risk	Difficult to judge. No protocol available. All outcomes mentioned in the methods section seemed to have been reported in the results section.