Ghasem Yadegarfar - Cancer Prevention Research Centre, Hope Hospital, & Epidemiology & Biostatistics Dept. School of Public Health, Isfahan University of Medical Sciences, Isfahan, Iran
Somaye Momenian - PhD candidate in Biostatistics, Cancer Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
Fateme Ibrahimi - MSc student in Epidemiology, Epidemiology & Biostatistics Dept. School of Public Health, Isfahan University of Medical Sciences, Isfahan, Iran
Mohammad Esmaeil Akbari - Cancer Research Centre, Shohada Hospital, Shahid Beheshti University of Medical Sciences, Tajrish, Tehran, Iran

Introduction & Aim: Breast cancer in women is a major health burden worldwide and the primary cause of cancer death among women globally. Although breastfeeding is known to protect against breast cancer, whether breastfeeding contributes to longer survival of breast cancer patients is unclear. Method: A cohort study was carried out on 846 parous women who recruited at Cancer Research Centre of Shahid Beheshti University of Medical Sciences (CRC of SBMU). The patients were visited and treated during 2005 to 2017 and followed up until March 2017. Data were collected from patients’ records kept at CRC and analysed with Cox Proportional Hazard Model using STATA14. Results: Median survival time was 3.1 year(Min=0.25&max=6.70). Five-year survival rate was 0.91(95%CI: 0.87-0.93). Univariate Cox regression analysis indicated women with more than 5 year duration of breast feeding had 3.67 times hazard ratio (HR) of death (HR=3.67,95% CI:1.47-8.70) than women with less than 18 months of breastfeeding; 55% excess hazard for women over 60 years old at diagnosis; an increasing pattern of HR for N classification(HR=1.80,3.93,4.54 for N1 to N3 categories respectively) and 157% excess hazard of death for women with more than 3 parities(HR=2.57,95% CI: 0.93,7.07).Adjusted Cox regression showed that still excess hazard ratio of death for highest breast feeding duration(HR=3.00,95% CI:0.88,10.24) and statistically significant pattern for N classification(HR from 1.83t 4.51). Conclusion: There was no strong evidence for effect of breastfeeding and parity on survival time and strong enough evidence for increasing pattern of hazard of death for women with higher N classification of breast cancer.

Breastfeeding, Cancer, Cohort, Parous