Breast density, already related to breast cancer risk, has been found to be an important indicator for cancer recurrence.
Research due to appear in the journal Cancer shows there is a greater risk of cancer coming back in women who have dense breasts.
The study, led by Dr Steven Narod of the Women’s College Research Institute in Toronto, was based on an analysis of 335 patients’ medical records, all of whom had undergone a lumpectomy for breast cancer.
The researchers determined the women’s breast density by studying their mammograms before treatment and classified them into three groups – low, medium and high density. They then looked at how many women in each group had a local recurrence of their cancer.
They found that, over a ten-year period, women who were in the high density group had a 16 per cent higher risk of breast cancer recurrence than those in the low density category.
The discrepancy was even greater for women with higher breast density who did not receive radiation treatment, with 40 per cent having a recurrence.
In contrast, none of those who had lower breast density and who also underwent radiation had a recurrence.
This suggests that additional therapies following surgery could be particularly beneficial for women with higher breast densities, the authors say, while patients with low breast density may not need radiation at all.
“The composition of the breast tissue surrounding the breast cancer is important in predicting whether or not a breast cancer will return after surgery,” Dr Narod concluded.
Commenting on the findings, Stephen Duffy, Cancer Research UK’s professor of screening, said: “This is intriguing. One reason for this could be that we know breast density increases the risk of a breast cancer in the first place, so it may simply increase the risk of a second one.
“Another possibility is that the dense tissue makes it more likely that other areas of cancer in the breast are not visible at initial diagnosis and so are not removed when surgery takes place.
“The potential to spare women, without dense tissue, radiotherapy is a very attractive prospect – but further studies will be necessary to be sure that this is safe practice.”
Cil, T., Fishell, E., Hanna, W., Sun, P., Rawlinson, E., Narod, S., & McCready, D. (2009). Mammographic density and the risk of breast cancer recurrence after breast-conserving surgery Cancer DOI: 10.1002/cncr.24638