Oral contraceptives

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Summary

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News Timeline

• Don't blame 'the pill' for estrogen in drinking water, Eurekalert.org, February 22, 2011.

Studies and Reports

• Figueiredo J et al., Oral contraceptives, postmenopausal hormones, and risk of asynchronous bilateral breast cancer: the WECARE Study Group, J Clin Oncol. 26(9):1411-8, March 20, 2008.
  • Conclusion. "This study provides no strong evidence that OC or PMH use increases the risk of a second cancer in the contralateral breast."
• Nyante S et al., The association between oral contraceptive use and lobular and ductal breast cancer in young women, Int J Cancer. 2008 Feb 15;122(4):936-41.
  • Abstract. "Recent reports indicate that the incidence of lobular breast cancer is increasing at a faster rate than ductal breast cancer, which may be due to the differential effects of exogenous hormones by histology. To address this issue, we examined whether the relationship between oral contraceptive use and incident breast cancer differs between lobular and ductal subtypes in young women. A population-based sample of in situ and invasive breast cancer cases between ages 20 and 44 were recruited from Atlanta, GA; Seattle-Puget Sound, WA and central New Jersey. Controls were sampled from the same areas by random-digit dialing, and were frequency matched to the expected case age distribution. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated using polytomous logistic regression. Among the 100 lobular cancers, 1,164 ductal cancers, and 1,501 controls, the odds ratios for oral contraceptive ever use were 1.10 (95% CI = 0.68-1.78) for lobular cancers and 1.21 (95% CI = 1.01-1.45) for ductal cancers, adjusted for study site, age at diagnosis, and pap screening history. Our results suggest that the magnitude of the association between ever use of oral contraceptives and breast cancer in young women does not vary strongly by histologic subtype. These results are similar to previous studies that report little difference in the effect of oral contraceptive use on breast cancer by histology."
• Kabat G et al., Oral contraceptive use, hormone replacement therapy, reproductive history and risk of colorectal cancer in women, Int J Cancer. 2008 Feb 1;122(3):643-6.
  • Abstract. "Evidence from epidemiologic studies suggests a possible role of exogenous and endogenous hormones in colorectal carcinogenesis in women. However, with respect to exogenous hormones, in contrast to hormone replacement therapy, few cohort studies have examined oral contraceptive use in relation to colorectal cancer risk. We used data from a large cohort study of Canadian women enrolled in a randomized controlled trial of breast cancer screening to assess the association of oral contraceptive use, hormone replacement therapy and reproductive factors with risk of colorectal cancer, overall and by subsite within the colorectum. Cancer incidence and mortality were ascertained by linkage to national databases. Among 89,835 women aged 40-59 at enrollment and followed for an average of 16.4 years, we identified 1,142 incident colorectal cancer cases. Proportional hazards models were used to estimate the associations between the exposures of interest and risk of colorectal cancer. Ever use of oral contraceptives at baseline was associated with a modest reduction in the risk of colorectal cancer (hazard ratio 0.83, 95% confidence interval 0.73-0.94), with similar effects for different subsites within the colorectum. No trend was seen in the hazard ratios with increasing duration of oral contraceptive use. No associations were seen with use of hormone replacement therapy (ever use or duration of use) or reproductive factors. Our results are suggestive of an inverse association between oral contraceptive use and colorectal carcinogenesis. However, given the lack of a dose-response relationship and the potential for confounding, studies with more complete assessment of exogenous hormone use throughout the life course are needed to clarify this association."
• Harris R et al, Oral contraceptives and breast cancer risk: a case-control study, Int J Epidemiol. 19(2):240-6, June 1990.
  • Abstract. "The association between breast cancer risk and oral contraceptive use was examined in 401 breast cancer patients and 519 hospital controls interviewed in New York City during 1979-1981. Control subjects were ascertained utilizing variable ratio matching to the cases (2:1 or 1:1) by sex, age, hospital, and time of diagnosis. No evidence of a positive association was found between cancer risk and the duration of use in either parous or nulliparous women. The odds ratios obtained by comparing users to non-users in women under 50 years of age after adjusting for other risk factors were 0.8 (95% CI = 0.4-1.4) for less than five years duration and 0.4 (95% CI = 0.2-0.8) for five or more years duration (P less than 0.05 when tested for decreasing trend). There was also no evidence of effect modification between oral contraceptive use and other breast cancer risk factors (viz. family history, nulliparity, late age at first pregnancy, or abstention from breastfeeding). Our results do not indicate that the use of oral contraceptives increases the risk of breast cancer."