The protective effect of parity in hormone receptor-positive, Ki-67 expressing breast cancer.
BACKGROUND
Epidemiologic studies showed that the experience of pregnancy is associated with a reduced risk of breast cancer. We hypothesized that parity may differentially be associated with the development of invasive breast cancer by each subtype.


METHODS
We reviewed the clinical, radiological, and pathological records of women diagnosed with invasive ductal carcinoma of the breast at Samsung Medical Center between 2005 and 2009. Clinicopathologic results were assessed by χ(2) and Fisher's exact tests with a Bonferroni correction for categorical variables, and by the Kruskal-Wallis test for nonparametric continuous variables. A multinomial logistic regression model was used for multivariate analysis.


RESULTS
Among a total of 3,095 patients, 283 (9.14 %) patients were nulliparous. Older age, higher pN, and expression of HER2 were associated with parity. In the analysis between parity and molecular subtypes, parity also had a variable influence on breast cancer subtypes (p = 0.032). Intergroup analysis with multiple comparison showed that luminal B subtype was related to nulliparity compared with HER2-positive subtypes (p = 0.03).


CONCLUSIONS
The effect of parity on the development of breast cancer differed by hormone receptor and HER2 expression. It seems that parity might have a protective effect against hormone receptor-positive breast cancer, especially cancers expressing HR+ and Ki-67. Further basic research to define and understand this result is ongoing.
Division of Breast and Endocrine Surgery, Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Irwon-dong, Gangnam-gu, Seoul, 135-710, Korea, sekyung.lee@samsung.com.
Se Kyung
SK
Lee
Seok Won
SW
Kim
Sang-Ah
SA
Han
Won Ho
WH
Kil
Jeong Eon
JE
Lee
Seok Jin
SJ
Nam
D000328:Adult; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000378:metabolism* / Q000473:pathology; D005260:Female; D006801:Humans; D019394:Ki-67 Antigen / Q000096:biosynthesis*; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D010298:Parity; D065840:Protective Factors; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000096:biosynthesis*; D012189:Retrospective Studies
D019394:Ki-67 Antigen; D018719:Erb-b2 Receptor Tyrosine Kinases; C508053:ERBB2 protein, human