London: Infertility and hormonal fertility treatments are likely to influence the amount of dense tissue in the breast and increase the potential risk of breast cancer, warns a new study.
The findings showed that women with a history of infertility had higher absolute dense volume -- that is more dense, fibroglandular breast tissue -- than non-infertile women.
Among infertile women, those who had undergone controlled ovarian stimulation (COS) -- the hormone treatment required for in vitro fertilisation -- had higher absolute dense volume than those who had not received any hormone treatment.
"The results from our study indicate that infertile women, especially those who undergo COS, might represent a group with an increased breast cancer risk," said lead author Frida Lundberg at Karolinska Institutet in Sweden.
Hormone replacement therapy, like COS, increases estrogen and progesterone levels and has been suspected to increase breast cancer risk.
The study, published in the open access journal Breast Cancer Research, is the first population-based analysis to investigate the effect of infertility and hormone stimulation on mammographic density, which may be a useful marker for the effect of hormonal fertility treatment on breast cancer risk, especially in women below the age at which breast cancer is normally diagnosed (50 years and older).
The researchers selected 43,313 women aged between 40 and 69 years who had mammograms between 2010 and 2013.
Out of 8,963 women who reported fertility problems, 1,576 had undergone COS, 1,429 had hormonal stimulation without COS and 5,948 had received no fertility treatment.
The team first compared mammographic density levels between fertile and infertile women. They then compared infertile women who had never received hormonal fertility treatment to those who had.