London: Two different classes of inexpensive, generic drugs can each reduce the recurrence of breast cancer and the risk of dying from the disease in postmenopausal women, according to two new studies.
The studies, both published in The Lancet, suggest that two types of drugs, aromatase inhibitors (AIs) and bisphosphonates, can be used together, increasing the benefits while also decreasing some side-effects.
The first study included evidence from 30,000 postmenopausal women in 9 randomised trials, showing that five years of treatment with an AI produces somewhat better survival in breast cancer than five years of standard endocrine therapy (tamoxifen).
Compared to tamoxifen, taking AIs for five years further reduced the likelihood of the breast cancer recurring by about 30 per cent, and the risk of dying from it by around 15 per cent throughout the decade after beginning treatment.
The researchers estimate that, compared to no endocrine treatment, the risk of dying from breast cancer for women who took AIs would be reduced by around 40 per cent in the decade after beginning treatment. The study's lead author was Mitch Dowsett of The Royal Marsden and The Institute of Cancer Research, UK.
The second study included evidence from almost 20,000 women in 26 randomised trials, showing that 2-5 years of treatment with bisphosphonates, class of drugs used to treat osteoporosis, reduces the risk of breast cancer recurring in post-menopausal women, and also significantly extends survival.
The most common site for breast cancers to spread to is bone. Tumour cells released from the primary breast cancer can remain dormant in the bone for years before spreading to other parts of the body.
Bisphosphonates alter the bone microenvironment, which could make it less favourable for cancer cells and so reduce the risk of cancer recurrence in the bone and in other organs.
The meta-analysis included patient data on 18,766 women in 26 randomised trials, comparing between two and five years of bisphosphonates versus no bisphosphonate.
In the overall study population, the only clear benefit of bisphosphonates was a 17 per cent reduction in recurrence of cancer in the bone.
However, among postmenopausal women, bisphosphonate treatment produced a larger reduction in bone recurrence of 28 per cent and also reduced the risk of dying from breast cancer by 18 per cent during the first decade after diagnosis.
"Our results show that adjuvant bisphosphonates in postmenopausal women prevent around a quarter of bone recurrences and one in six of all breast cancer deaths in the first decade of treatment," said bisphosphonate study's lead author Robert Coleman, from the University of Sheffield, UK.
Richard Gray from the University of Oxford and lead statistician for both studies, noted that the two types of drugs are complementary, because the main side effect of aromatase inhibitors is an increase in bone loss and fractures, while bisphosphonates reduce bone loss and fractures as well as improving survival
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