Reproductive Factors and Breast Cancer - Parity, Breastfeeding and Genetic Predisposition in Relation to Risk and Prognosis

Sammanfattning: The aim of this thesis was to study reproductive factors and genetic polymorphisms in relation to breast cancer risk and survival. An important component of this was to investigate the risk of specific breast cancer subgroups. The association between parity and breast cancer-specific survival was studied among 4,453 women diagnosed with breast cancer in Malmö, Sweden. It was found that: • Nulliparity and multiparity (?4 children) were associated with a worse survival after breast cancer than that of women with one child. Parity, age at first childbirth and breastfeeding were examined in relation to the risk of specific breast cancer subgroups among 17,035 women in The Malmö Diet and Cancer Study. It was found that: • Nulliparous women had a higher risk of more aggressive breast cancer subgroups than women with one child. • Women with a late first childbirth (>30 years) had a higher risk of more aggressive breast cancer subgroups than women with an early first childbirth (?20 years). • Long duration of breastfeeding was associated with relatively aggressive breast cancer subgroups. The potential interaction between parity/age at first childbirth and single nucleotide polymorphisms (SNPs) was studied in The Malmö Diet and Cancer Study. It was found that: • Seven out of 14 investigated SNPs showed a statistically significant association with breast cancer risk. Certain combinations of parity/age at first childbirth and SNPs might alter the susceptibility to breast cancer. We conclude that parity, breastfeeding and genetic predispostion are related to breast cancer risk and/or prognosis.