Table 1. Studies reporting no increase in the risk of breast cancer associated with COC use.

	Study design	Risk analysis results
Jordan et al [12]	Case–Control Study	0.7% of all cases is attributable to COC use
CDC [13]	Case–Control Study	RR: 0.6–1.6 (not significant)
Nurses’ Health Study [14]	Prospective Cohort Study	>10 year COC use RR: 1.11 (95% CI: 0.94–1.32)
Marchbanks et al [15]	Case–Control Study	Current use; RR: 1.0 (95% CI: 0.8–1.3) Past use; RR: 0.9 (95% CI: 0.8–1.0)
Michels et al [16]	Prospective Cohort Study	>10 year COC use RR:1.04 (0.97, 1.11)
Oxford-FPA [5]	Prospective Cohort Study	Ever versus Never RR: 1.0 (95% CI: 0.9–1.1)
RCGP [17]	Prospective Cohort study	Ever versus Never RR: 0.98 (95% CI: 0.87–1.1)

RR: Risk Ratio; COC: Combined Oral Contraceptive; CI: Confidence Interval; CDC: Centres for Disease Control; Oxford FPA: Oxford Family Planning Association; RCGP: Royal College of General Practitioners