Breastfeeding increased risk her2+ bc...

[RobinP]

Breastfeeding was associated with a 4-fold increased risk only for breast cancer that overexpressed HER-2/neu in this particular article:

http://cebp.aacrjournals.org/cgi/content/full/9/1/65

Also, prolactin protects bc cells against apoptosis or cell death:
http://www.nature.com/bjc/journal/v91/n2/abs/6601947a.htm

Also, oxytocin has a antiproliferative effect on bc cells through the PKA pathway, which inhibits Ras and proliferation:
http://www.ncbi.nlm.nih.gov/sites/en...&dopt=Abstract

PS I breastfeed about a year before I got bc. Interesting.

[RhondaH]

and was dx (weakly HER2+) on 2/05. Interesting.

Rhonda

[Christine MH-UK]

"Breastfeeding for at least 1 year was inversely associated with HER-2/neu+ breast cancer [OR, 0.3; 95% confidence interval (CI), 0.1–0.7] more so than HER-2/neu- breast cancer (OR, 0.8; 95% CI, 0.5–1.2)."

In plain English:
'Inversely associated' means breastfeeding decreased the incidence of Her2/neu+. The .3 means that women who breastfed for at least a year got only 30% as much her2 positive breast cancer as those who didn't (although this is an estimate and the actually amount is likely to be between 10% to 70% as much). In contrast, breast feeding women had 80% as much her2 neu negative breast cancer (a reduction, but not as big a reduction as for her2 positive women) and although it is possible that breast feeding may halve breast cancer in this group, it is also possible that it doesn't make a difference.

So, why do women who have breast fed sometimes get her2+ positive cancer? Well, even if breast feeding women had only a third the incidence of breast cancer, there will still be alot of women in that one third. Also the mutation that caused the breast cancer may have occurred before breast feeding.