How does the duration of use of oral contraceptives affect a woman's risk for breast cancer?

Updated: Dec 26, 2019
  • Author: Graham A Colditz, MD, DrPH; Chief Editor: Chandandeep Nagi, MD  more...
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Most studies have observed no significant increase in breast cancer risk with long durations of use. Individual data from 54 epidemiologic studies were collected and analyzed centrally. In this large pooled analysis, data from 53,297 women with breast cancer and 100,239 women without breast cancer were evaluated, and no overall relationship was observed between duration of use and risk of breast cancer. Current and recent users of oral contraceptives had a significantly increased risk of breast cancer (RR for current vs never users = 1.24; 95% CI, 1.15-1.33). [38] This increased risk subsided within 10 years of stopping oral contraceptive use (RR by years since stopping use vs never use: 1-4 years, 1.16; 5-9 years, 1.07; 10-14 years, 0.98; >15 years, 1.03).

A modestly increased risk of breast cancer was observed among current and recent oral contraceptive users, and no independent effect of long duration of use on risk of breast cancer was observed, even among very young women. Thus, the increased risk of breast cancer observed among young long-term oral contraceptive users in past individual studies appear primarily due to recent use of oral contraceptive rather than to duration of use. These data suggest that oral contraceptives may act as late-stage promoters. Table 1 summarizes the excess cases of breast cancer that would be generated in a population of 10,000 women using oral contraceptives at different ages.

Table 1. Excess Cases of Breast Cancer Due to Use of Oral Contraceptives for 5 Years [38] (Open Table in a new window)

Age at Starting Use, y

Cases Among Users

Cases Among Nonusers

Cumulative Excess Cases per 10,000

16-19

4.5

4

0.5

20-24

17.5

16

1.5

25-29

48.7

44

4.7

30-34

110

100

11.1

35-39

180

160

21

40-44

260

230

32


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