Table 1 The characteristics of studies (case-control and cohort) on multiple births and maternal breast cancer risk
Authors (Years) (R) | Type of Study (country) | Sample Size Case or exposed/ control or non-exposed | Study population | Mean age Mean BMI | Incidence breast cancer | Effect size (% 95 CI) | NOS Score |
|---|---|---|---|---|---|---|---|
I.M. Krul et al., 2014 | Cohort (Netherlands) | 12,589 (women who had been treated with IVF and completed a risk factor questionnaire) 1688 (with Multiple birth) 10,901 (without Multiple birth) | Dutch women who had been treated with IVF between 1983 and 1995 and completed a risk factor questionnaire between 1997 and 1999 | 32.9 NR | 317 (57 had multiples) | Adjusted hazard ratio (HR) (95% CI): Multiple birth: 1.44 (1.06–1.97) Twins 1.33 (0.95–1.86) Triplets/quadruplets/two multiples 2.19 (1.21–3.94) | 8 |
R. Troisi et al., 2012 | Case-control (Norway, Sweden And Denmark) | 15,609 women 1419 case (women born in Norway, Sweden or Denmark who were subsequently diagnosed with primary, invasive breast cancer) 14,190 controls (women without breast cancer from the national birth registries matched on birth country, birth year and vital status) | Norwegian, Swedish and Danish Women | 32.3 NR | NR | Relative risk (RR) for multiple gestation (95% CI) = 0.81 (0.53–1.23) | 7 |
Lauren E. B. et al., 2018 | prospective cohort (USA) | 50,983 women 1583 with Twin/triplets 49,400 without Twin/triplets | African American women | 41.5 28.3 | 1583 breast cancer cases among 50,983 cases | Multivariable hazard ratio (MV HR) for Twin/triplet (95% CI): 1.18 (0.84, 1.66) | 8 |
Wyshak et al., 1983 | Cohort (USA) | Multiple births 3982 Without Multiple births 3982 | Connecticut twin registry and Connecticut tumor registry | 59 NR | 0.6% on the basis of incidence rates for white females in Connecticut, 1973-77 | Relative risk (RR) for Mothers of Dizygotic Twins: RR = 3.2 (1.12, 11.16) | 8 |
Lambe et al., 1996 | nested case-control (Swede) | Multiple births/breast cancer 329/19,368 Multiple births/control 2,031/100,459 | Swedish Cancer Registry and a nationwide Fertility Registry | NR NR | NR | Breast cancer risk in mothers with multiple live births: OR = 0.88 (0.78, 0.99) | 7 |
Murphy et al., 1997 | nested case – control (UK) | Multiple births/breast cancer 64/4,790 Multiple births/control 895/46,751 | Swedish cancer registry | NR NR | NR | breast cancer risk in mothers of twins: OR = 0.71 (95% confidence interval 0.55–0.91) | 7 |
Albrektsen et al., 1995 | Cohort (Norway) | Multiple births/breast cancer 97/4,782 Singleton births/breast cancer 4,685/4,782 | Cancer registry of Norway | NR NR | 4,782 cases with breast cancer of 802,269 parous Norwegian women | risk of breast cancer among women ever having had a twin birth: RR = 0.89 (95% CI = 0.73–1.09) risk of breast cancer among women ever having had a multi birth: RR = 1.48 (95% CI = 0.97–2.25) | 8 |
Wohlfahrt et al., 1999 | Cohort (Denmark) | Multiple births/breast cancer 168/9,495 Singleton births/breast cancer 9,327/9,495 | Danish cancer registry | NR NR | 9,495 incident cases of breast cancer of 998,499 women | Risk of breast cancer in Mothers having a multiple birth: Relative risk (RR) = 1.8; 95% confidence interval (CI) = 1.1–2.8). | 8 |
Neale et al., 2004 | retrospective cohort study (Swede) | Breast cancer/multiple births 178/5,080 Breast cancer/singleton births 358/10,181 | Utah population database Utah cancer registry | 62.8 NR | No. of breast cancer cases 178 among 5080 twin mothers | Adjusted RR (95% CI) = 1.02 (0.85–1.22) | 8 |
Neale et al., 2004 | Cohort (Swede) | Multiple births/breast cancer 116/6,309 Singleton births/breast cancer 6,193/6,309 | Swedish civil birth register Swedish cancer registry | 40.1 NR | 6309 breast cancer cases (116 of them were twin mothers) | Adjusted RR (95% CI) = 0.91 (0.75–1.09) p-value = 0.27 | 8 |
Ji et al., 2007 | Cohort (Swede) | Breast cancer/multiple births 1,010/30,409 Breast cancer/singleton births 57,080/1500,000 | Swedish family cancer database | NR NR | 1010 breast cancer case in 30,409 twin women | RR = 0.85, 95% CI (0.74–0.98) | 7 |
Polednak et al. 1983 | Case-control (USA) | Breast cancer 314 Control 314 | Cancer registry in New York state | NR NR | NR | OR = 1.33 (0.38, 4.66) | 7 |
Olsen et al. 1988 | Case-control (Denmark) | Breast cancer 5,213 Control 20,025 | Denmark cancer registry, medical birth registry | NR NR | 5213 breast cancer that 141 twins | OR = 1.07 (0.88, 1.30) | 7 |
Innes et al. 2004 | Case-control (USA) | Breast cancer 2,522 Control 10,052 | New York state birth and tumor registries | 37.6 NR | 2522 breast cancer 32 twins | OR = 1.43 (0.75, 2.73) | 7 |
Nasca et al. 1992 | Case-control (USA) | Breast cancer 2,561 Control 2,616 | Two case studies conducted in New York state | NR NR | 2561 breast cancers 79 twins | OR = 1.05 (0.77, 1.44) | 8 |
Hsieh et al. 1993 | Case-control (USA) | Breast cancer 2,821 Control 8,882 | International case–control studies | NR NR | 2733 breast cancers 88 twins | OR = 1.21 (0.94, 1.55) | 7 |
Dietz et al. 1995 | Case-control (USA) | Breast cancer 5,880 Control 8,217 | Tumor registries in Wisconsin, western Massachusetts, Maine and New Hampshire | NR NR | 5880 breast cancer 146 twins | OR = 0.94 (0.75, 1.17) | 7 |
La Vecchia et al. 1996 | Case-control (Italy) | Breast cancer 2,569 Control 2,588 | Large case–control studies conducted in six regions of Italy | 55 NR | 2569 breast cancers 38 twin birth | OR = 0.74 (0.51, 1.07) | 7 |
Triosi et al., 1998 | Case-control (USA) | Breast cancer 1,239 Control 1,166 | US cancer registry covering Atlanta, GA; Seattle, WA; New Jersey | NR NR | 1239 breast cancers 35 twins | OR = 0.94 (0.58, 1.51) | 7 |