According to breast cancer researchers, the types of breast cancer, which are being detected by screening, has changed over the past decades.
There seem to be more cases of slow-growing tumours and oestrogen-receptor positive cancers nowadays than in the past. This could depend from various factors, including the fact that with the improved screening methods cancers are now detected earlier and cannot develop into fast growing tumours.
Other researchers deduce that tumours are becoming more hormone-dependant than in the past that is why many react positively to hormone treatments, such as tamoxifen, which prevent the tumour from reforming. There is also a higher survival rate in women with breast cancer as opposed to the past.
It has been suggested that the changes in our way of life could lead to the increase of hormone-dependent tumours in women who suffer from obesity, menopause conditioned by hormone treatment and the fact that women are having babies at an older age.
Although these factors could influence the change of tumour-types, further studies must be conducted in order to verify this data. It is still not clear whether there is an actual change in tumour types or if it is the method of screening which better detects certain types of tumours rather than others.