Nanthini Balakrishnan1, Soo-Hwang Teo2, Siamala Sinnadurai1, Nanthini Thevi Bhoo Pathy1, Mee-Hoong See3, Nur Aishah Taib3, Cheng-Har Yip2,4, Nirmala Bhoo Pathy5,6. 1. Julius Centre University of Malaya, Department of Social and Preventive Medicine, Faculty of Medicine, University of Malaya, Lembah Pantai, 50603, Kuala Lumpur, Malaysia. 2. Cancer Research Malaysia, 1 Jalan SS12/1A, 47500, Subang Jaya, Selangor, Malaysia. 3. Department of Surgery, Faculty of Medicine, University of Malaya, Lembah Pantai, 50603, Kuala Lumpur, Malaysia. 4. Subang Jaya Medical Centre, 1 Jalan SS12/1A, 47500, Subang Jaya, Selangor, Malaysia. 5. Julius Centre University of Malaya, Department of Social and Preventive Medicine, Faculty of Medicine, University of Malaya, Lembah Pantai, 50603, Kuala Lumpur, Malaysia. ovenjjay@gmail.com. 6. Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, P.O. Box 85500, 3508 GA, Utrecht, The Netherlands. ovenjjay@gmail.com.
Abstract
BACKGROUND: Reproductive factors are associated with risk of breast cancer, but the association with breast cancer survival is less well known. Previous studies have reported conflicting results on the association between time since last childbirth and breast cancer survival. We determined the association between time since last childbirth (LCB) and survival of women with premenopausal and postmenopausal breast cancers in Malaysia. METHOD: A historical cohort of 986 premenopausal, and 1123 postmenopausal, parous breast cancer patients diagnosed from 2001 to 2012 in University Malaya Medical Centre were included in the analyses. Time since LCB was categorized into quintiles. Multivariable Cox regression was used to determine whether time since LCB was associated with survival following breast cancer, adjusting for demographic, tumor, and treatment characteristics. RESULTS: Premenopausal breast cancer patients with the most recent childbirth (LCB quintile 1) were younger, more likely to present with unfavorable prognostic profiles and had the lowest 5-year overall survival (OS) (66.9; 95% CI 60.2-73.6%), compared to women with longer duration since LCB (quintile 2 thru 5). In univariable analysis, time since LCB was inversely associated with risk of mortality and the hazard ratio for LCB quintile 2, 3, 4, and 5 versus quintile 1 were 0.53 (95% CI 0.36-0.77), 0.49 (95% CI 0.33-0.75), 0.61 (95% CI 0.43-0.85), and 0.64 (95% CI 0.44-0.93), respectively; P trend = 0.016. However, this association was attenuated substantially following adjustment for age at diagnosis and other prognostic factors. Similarly, postmenopausal breast cancer patients with the most recent childbirth were also more likely to present with unfavorable disease profiles. Compared to postmenopausal breast cancer patients in LCB quintile 1, patients in quintile 5 had a higher risk of mortality. This association was not significant following multivariable adjustment. CONCLUSION: Time since LCB is not independently associated with survival in premenopausal or postmenopausal breast cancers. The apparent increase in risks of mortality in premenopausal breast cancer patients with a recent childbirth, and postmenopausal patients with longer duration since LCB, appear to be largely explained by their age at diagnosis.
BACKGROUND: Reproductive factors are associated with risk of breast cancer, but the association with breast cancer survival is less well known. Previous studies have reported conflicting results on the association between time since last childbirth and breast cancer survival. We determined the association between time since last childbirth (LCB) and survival of women with premenopausal and postmenopausal breast cancers in Malaysia. METHOD: A historical cohort of 986 premenopausal, and 1123 postmenopausal, parous breast cancerpatients diagnosed from 2001 to 2012 in University Malaya Medical Centre were included in the analyses. Time since LCB was categorized into quintiles. Multivariable Cox regression was used to determine whether time since LCB was associated with survival following breast cancer, adjusting for demographic, tumor, and treatment characteristics. RESULTS:Premenopausal breast cancerpatients with the most recent childbirth (LCB quintile 1) were younger, more likely to present with unfavorable prognostic profiles and had the lowest 5-year overall survival (OS) (66.9; 95% CI 60.2-73.6%), compared to women with longer duration since LCB (quintile 2 thru 5). In univariable analysis, time since LCB was inversely associated with risk of mortality and the hazard ratio for LCB quintile 2, 3, 4, and 5 versus quintile 1 were 0.53 (95% CI 0.36-0.77), 0.49 (95% CI 0.33-0.75), 0.61 (95% CI 0.43-0.85), and 0.64 (95% CI 0.44-0.93), respectively; P trend = 0.016. However, this association was attenuated substantially following adjustment for age at diagnosis and other prognostic factors. Similarly, postmenopausal breast cancerpatients with the most recent childbirth were also more likely to present with unfavorable disease profiles. Compared to postmenopausal breast cancerpatients in LCB quintile 1, patients in quintile 5 had a higher risk of mortality. This association was not significant following multivariable adjustment. CONCLUSION: Time since LCB is not independently associated with survival in premenopausal or postmenopausal breast cancers. The apparent increase in risks of mortality in premenopausal breast cancerpatients with a recent childbirth, and postmenopausal patients with longer duration since LCB, appear to be largely explained by their age at diagnosis.
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