Akahira 2001.

Study characteristics
Methods	Multicentre retrospective analysis: 24 Japanese institutions received questionnaires regarding stage IV epithelial ovarian cancer women
Participants	225 women with stage IV ovarian cancer whose disease had been confirmed by exploration and only women with complete medical records were included. Stage IV disease was defined according to FIGO. Only women who underwent an initial attempt at surgical debulking were analysed. The median age in the study was 54 years (range: 26 to 85 years) All 225 women had FIGO stage IV disease Histological cell type: serous: 136 (60.5%), mucinous: 16 (7%), clear cell 26 (11.5%), endometrioid 27 (12%), transitional 4 (2%), undifferentiated 12 (5%), other 4 (2%) Extent of disease: pleural effusion: 89 (39.5%), liver: 34 (15%), lung: 8 (3.5%), lymph node: 44 (19.5%), other: 15 (6.5%), multiple sites: 35 (15%) Performance status: 0: 26 (11%), 1: 76 (34%), 2: 49 (22%), 3: 67 (30%), 4: 7 (3%)
Residual disease details	Intervention group: 'Optimal' cytoreduction was defined as no gross residual tumour greater than 2 cm in diameter Comparison group: LVRD was defined as any gross residual disease remaining greater than 2 cm in diameter
Outcomes	Overall survival: HR adjusted for histology and performance status: < 2 cm versus > 2 cm; HR 0.42 (95% CI 0.31 to 0.64), or > 2 cm vs < 2c m; HR 2.39 (95% CI 1.68 to 3.40) so that reference group is consistent throughout review Adverse events; median blood loss, blood transfusions
Risk of bias (QUIPS)	1. Study participation (a‐f): low risk Adequate number of participants and description of target population. Baseline characteristics, eligibility criteria, sampling frame and period/place study took place presented clearly. 2. Study attrition (a‐e): unclear risk Unclear if patients with incomplete follow‐up were excluded before arriving at the stated sample size. Insufficient information to permit judgement. 3. Prognostic factor measurement (a‐f): unclear risk Valid and reliable measurement of RD. Multicentre design may introduce heterogeneity in measurement of RD Outcome level assessment: Outcome: overall survival 4. Outcome measurement (a‐c): low risk Valid and reliable measurement of outcome 5. Adjustment for other prognostic factors (a‐g): high risk HR for OS was adjusted for histology, performance status and RD in multivariable Cox model 6. Statistical analysis and reporting (a‐d): unclear risk In methods, authors reported that significant variables from the univariate analysis were included in the multivariable model Outcome: progression‐free survival Not reported
Notes	There were 70 women (31.1%) in the 'optimal' group and 155 (68.9%) in the LVRD group The median follow‐up time was 47.5 months (range: 13 to 112 months) The median survival for all women with stage IV ovarian cancer was 20 months, with an estimated 5‐year survival rate of 19.6% Mean survival in the optimal group was 32 months and 16 months in the suboptimal group (P < 0.0001) MV analysis included the histology and performance status as covariates in the model The median duration of the debulking surgery was 240 minutes (range: 40 to 780 minutes. The median estimated blood loss was 1085 mL (range 40 to 11,000 mL), and 112 women (50%) received blood transfusions intra‐ and postoperatively