Examining the Link Between Fertility Treatment and Breast Cancer

The recurrence of breast cancer in Elizabeth Edwards, who was in her forties when she conceived two children through assisted reproduction, have stoked fears that drugs used in fertility treatments may raise cancer risks.

Slate's Amanda Schaffer gives a nice rundown of the relevant literature, which suggests these fears are unfounded:

One study of Australian women, which appeared in the Lancet
in 1999, found that women who'd been exposed to fertility drugs for in vitro were more likely to be diagnosed with breast cancer in the year following treatment. [...] But crucially, when longer-term data were included, the in vitro group appeared no more likely to get breast cancer than women in the general population.

Happily, other papers do not find a link between fertility treatments and breast cancer risk. A 2004 French study, which followed women prospectively, found that with one likely chance exception, "treatment for infertility does not influence breast cancer risk overall." And a 2005 review paper, which scrutinized the safety of fertility drugs, concluded that to date, there has been "no evidence" to demonstrate "a direct association, let alone a causal relationship" between fertility drugs and cancer. All told, at least half a dozen studies dispel the worry that fertility treatments cause a significant increase in breast cancer risk.

Schaffer's fine article could, however, use one postscript: the breast cancer risks of fertility treatments may be small, but other risks appear to be real, and much more research is needed before the procedure is fully understood.

Pregnancy, fertility treatment and cancer [Slate]