Chan 2003.

Study characteristics
Methods	Retrospective cohort study
Participants	All consecutive cases of advanced‐stage epithelial ovarian carcinoma diagnosed in younger women (range 22 to 45 years) were identified from tumour registry databases and a comparable group of 52 women who averaged 21 years older (range 46 to 85 years) was selected as controls. One‐to‐one matching from the same database was performed based on the date of diagnosis and stage of disease during the same period in the same institution. Thus, the controls were similarly distributed across 17 years. The mean age at study entry was 50.5 years with a range between 22 and 85 years (40 (SD 5.7) and 61 years (SD 8.7) for younger and older women respectively) 5 (4.8%) women had FIGO stage IIIA, 5 (4.8%) had stage IIIB, 74 (71.1%) women had stage IIIC and 20 (19.2%) had stage IV disease Tumour cell type: papillary serous 72 (63.16%), mucinous: 3 (2.63%), endometrioid: 17 (14.9%), clear cell: 1 (0.88%), small cell: 3 (2.63%), undifferentiated: 8 (7%) Tumour grade: 1: 8 (7%), 2: 24 (21.1%), 3: 72 (63.2%) Performance status: 0: 65 (57%), 1 to 2: 35 (30.7%), unknown: 4 (3.51%)
Residual disease details	Residual disease was noted as follows: SVRD: 71 (62.3%) LVRD (> 1 cm): 43 (37.7%) Women were divided into SVRD (defined as optimal) and 1 cm or more (defined as suboptimal) groups based on residual disease after initial surgery. Optimal debulking was achieved in 36 (69%) and 35 (67%) women in younger in older groups respectively. All women received either a platinum/paclitaxel or a platinum/cyclophosphamide regimen for primary chemotherapy and women who underwent neoadjuvant chemotherapy with interval debulking were removed from the study. Gynaecology oncologists from the academic institution surgically staged all women.
Outcomes	A multivariable analysis which included older versus younger age, stage (IV vs III), performance status (1 to 2 vs 0) and residual disease (LVRD (> 1 cm) vs SVRD) was performed to evaluate all factors that were significant in the univariate analysis Overall survival: HR adjusted for prognostic categories (see above): LVRD (> 1 cm) vs SVRD HR 1.67 (95% CI 1.03 to 2.72)
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 Definition of OS not provided but no reason to doubt they used standard definition 5. Adjustment for other prognostic factors (a‐g): low risk HR for OS was adjusted for residual disease, age (older versus younger), stage (IV versus III) and performance status (1 to 2 versus 0) in a multivariable Cox model 6. Statistical analysis and reporting (a‐d): high risk No conceptual framework; unclear of variable selection criteria in multivariate model Outcome: progression‐free survival 4. Outcome measurement (a‐c): low risk Definition of PFS not provided but no reason to doubt they used standard definition 5. Adjustment for other prognostic factors (a‐g): high risk PFS was reported in table comparing younger vs older patients but was not used in any multivariable modelling 6. Statistical analysis and reporting (a‐d): high risk There was only a multivariate model for OS but not PFS
Notes	The median follow‐up after surgery was 33 months (range 6 to 142 months) 5‐year survival: of younger and older women: SVRD: 59% and 21% in young and old women respectively, LVRD (> 1 cm): 28% and 22% in young and old women respectively Median survival: SVRD: 66 months and 45 in young and old women respectively, LVRD (> 1 cm): 37 and 19 months in young and old women respectively, P = 0.003   Other variables in Cox model: Older versus younger age (HR 1.82, 95% CI 1.09 to 3.05), stage IV versus stage III disease (HR 3.00, 95% CI 1.71 to 5.25), performance status 1 to 2 versus 0 (HR 1.89, 95% CI 1.13 to 3.15) Despite the higher prevalence of poorly differentiated tumours in the older group, tumour grade (3 versus 1 to 2) was not an important prognostic factor in multivariable analysis (HR 1.06, 95% CI 0.57 to 1.97)