Early detection of second breast cancers halves women's risk of death

A group of international researchers has found the first reliable evidence that early detection of subsequent breast tumours in women who have already had the disease can halve the women's chances of death from breast cancer.

According to the research published online today (Wednesday 18 March) in the cancer journal, Annals of Oncology [1], if the second breast cancer was picked up at its early, asymptomatic stage, then the women's chances of survival were improved by between 27-47% compared to women whose second breast cancer was detected at a later stage when symptoms had started to appear.

Until now, the impact of early detection of second breast cancers was unclear. Attempts to investigate it have been complicated by the fact that it is not possible to run randomised controlled trials because women who have already had one breast cancer are at higher risk of a relapse or a second breast cancer and, therefore, are generally advised to have regular breast checks as part of their follow-up care. What studies there have been have not made adjustments for the main factors that could bias the findings from a non-randomised study and often have looked at breast cancers occurring in either the same breast (ipsilateral relapse) or the other breast (contralateral) but not either breast.

The current study looked at 1,044 women who had attended one clinical centre in Florence (Italy) between 1980-2005 and who had developed a second breast cancer. In that time 455 women had ipsilateral breast cancers (IBC) diagnosed and 589 women had contralateral breast cancers (CBC) diagnosed. Of these second cancers, 699 (67%) were asymptomatic and 345 (33%) were symptomatic.

The researchers found that mammography was more sensitive than clinical examination for detecting second cancers (86% versus 57%). However, 13.8% of cases were only detected by clinical examination. Asymptomatic cancers were smaller than symptomatic for both IBC and CBC; early stage cancers were more frequent in asymptomatic (58.1%) than in symptomatic (22.6%) women; and fewer women with asymptomatic than symptomatic CBC had node metastases (an indicator that the cancer may have spread).

In the analysis of the results, the researchers (from Italy, Australia and the UK) adjusted to allow for lead-time bias (bias caused by an earlier detection of the cancer) and length-time bias (bias caused by the fact that some breast cancers develop more slowly than others and, therefore, are more likely to be detected at the asymptomatic stage and are less likely to cause death).

Associate Professor Nehmat Houssami, a breast physician and principle research fellow at the University of Sydney's School of Public Health, Australia, who led the study, said: "Intuitively, it makes sense to consider that early detection of second breast cancers will improve prognosis, since breast cancer survivors have a long-term risk of developing further disease or relapse in either breast. However, due to a paucity of evidence about this until now, current recommendations on surveillance of breast cancer survivors vary substantially between countries and organisations.