Use of Oral Contraceptives and Breast Cancer Survival

Introduction: Oral contraceptives (OC) have been shown to give a transient increased breast cancer risk. However, studies on breast cancer survival after OC use are sparse and conflicting.Aim: The aim of this study was to examine previous use of OC in relation to survival after breast cancer diagnosis.Methods: Data was collected from Malmö Diet and Cancer Study, with baseline examinations between 1991 and 1996. Out of 17035 women who completed all study parts, 765 women with incident breast cancer were included in this study. Kaplan Meier and Cox Proportional Hazards analyses, with 95% confidence intervals (CI), were used to study OC in relation to breast cancer-specific and overall survival. All analyses were stratified on age at diagnosis.Results: Women who had ever used OC were younger and more often had grade III tumors than those who had never used OC. Breast cancer-specific survival in women who ever had used OC was better when adjusting for BMI, socioeconomic status as well as tumor characteristics. However, when adjusting for age at diagnosis, the results did not remain significant (0.68, CI 95% 0.39- 1.18). Stratified analyses on age at diagnosis (40-55, 56-70 and ≥ 71) showed no statistically significant associations.Conclusion: In this study we could not demonstrate a significant effect of OC use on breast cancer survival