Table 1.
Characteristics of all included studies regarding association between metformin use and risk of gynecologic cancer.
| References | Study design | Country | Sample size/ mean age | Cancer cases | Cancer type | a history of metformin use before the cancer diagnosis | continued the metformin use during treating cancer | BMI | waist | blood glucose | hyperlipidemia | Adjusted variables | Results (OR/RR, 95%CI) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Becker et al. 2013 (18) | Case-control | UK | 17878/ 63.0 | 2554 | EC | Yes | NR | NR | NR | DM | NR | BMI, smoking, DM | OR: 0.86 (0.63-1.18) |
| Luo et al. 2014 (24) | Cohort | USA | 88107/ 63.0 | 1241 | EC | Yes | Yes | NR | NR | DM | NR | Age, BMI, race, education, smoking, physical activity, alcohol intake, HRT, oral contraception use, parity, age at first birth, different treatment assignments for clinical trials | RR: 1.64 (0.92-2.91) |
| KO et al. 2015 (26) | Cohort | USA | 541128/ NR | 729 | EC | Yes | Yes | NR | NR | DM | NR | Age, Charlson index, fibroid, infertility, PCOS, DM, hypertension, endometrial hyperplasia, connective tissue disease, oral contraception use, HRT, ultrasound | RR: 1.09 (0.88-1.35) |
| Tseng et al. 2015 (27) | Cohort | Taiwan, China | 478921/55.6 | 2885 | EC | Yes | Yes | NR | NR | DM | NR | Age, hypertension, COPD, stroke, heart disease, obesity, metabolic profiles, various drugs | RR: 0.68 (0.61-0.74) |
| Franchi et al.2016 (28) | Case-control | Italy | 7861/ 64 | 376 | EC | Yes | NR | NR | NR | DM | NR | Age, date at cohort entry, duration of follow-up, the Charlson comorbidity index, cardio/cerebrovascular diseases, various drugs, HRT, oral contraception use | OR: 0.99 (0.80-1.23) |
| Gong et al. 2016 (19) | Cohort | USA | 145826/ NR | 993 | EC | Yes | Yes | NR | NR | DM | NR | Age, race, education, smoking, physical activity, aspirin, hyperlipidemia, HRT, BMI, WHR | RR: 1.24 (0.90-1.70) |
| Arima et al. 2017 (20) | Case-control | Finland | 12382/ NR | 590 | EC | Yes | NR | NR | NR | DM | NR | Age, DM, various drugs | OR: 1.24 (1.02-1.51) |
| Bodmer et al. 2011 (21) | Case-control | UK | 10781/ 61.2 | 1611 | OC | Yes | NR | NR | NR | DM | NR | BMI, smoking, HRT, oral contraception use, history of hysterectomy, endometriosis and PCOS | OR: 0.61 (0.30-1.25) |
| Tseng et al. 2015 (22) | Cohort | Taiwan, China | 479475/ 55.6 | 3201 | OC | Yes | Yes | NR | NR | DM | NR | Age, hypertension, COPD, stroke, obesity, eye disease, nephropathy, ischemic heart disease, peripheral arterial disease, dyslipidemia, urinary tract disease, other cancers, various drugs | RR: 0.66 (0.59-0.73) |
| Gong et al. 2016 (19) | Cohort | USA | 145826/ NR | 553 | OC | Yes | Yes | NR | NR | DM | NR | Age, race, education, smoking, physical activity, aspirin use, hyperlipidemia, HRT, BMI, WHR | RR: 1.06 (0.64-1.74) |
| Urpilainen et al. 2018 (23) | Cohort and case-control | Finland | 137643/ NR | 303 | OC | Yes | Yes | NR | NR | DM | NR | Age, duration of DM | RR: Cohort: 1.02 (0.72-1.45) Case-control: 0.91 (0.61-1.34) |
| Tseng et al. 2016 (25) | Cohort | Taiwan, China | 139911/ 58.2 | 476 | CC | Yes | Yes | NR | NR | DM | NR | Age, hypertension, COPD, stroke, obesity, eye disease, nephropathy, ischemic heart disease, peripheral arterial disease, dyslipidemia, urinary tract disease, other cancers, various drugs | RR: 0.56 (0.40-0.78) |
OR, odds ratio; RR, relative risk; CI, confidence interval; NR, not reported; OC, ovarian cancer; EC, endometrial cancer; CC, cervical cancer; BMI, body mass index; DM, diabetes mellitus; HRT, hormone replacement therapy; PCOS, polycystic ovarian syndrome; COPD, chronic obstructive pulmonary disease; WHR, waist-to-hip ratio.