UK researchers found that treatment with the chemotherapy agent doxorubicin followed with the bisphosphonate drug zoledronic acid slowed down the growth of breast tumours in early studies.
A clinical trial in humans is now under way and it is possible that it could lead to the treatment becoming widely available to patients.
Zoledronic acid is relatively cheap costing under £1,000 per year of treatment - less than 1/20th the price of Herceptin - so the treatment should be affordable on the NHS, the papers add.
Osteoporosis drug shrank breast cancer tumours in mice
What is the research?
The findings are based on a study of mice genetically engineered with human breast cancer cells.
The mice were divided into equal groups and injected weekly for six weeks with either doxorubicin, zoledronic acid, doxorubicin followed by zoledronic acid 24 hours later or zoledronic acid followed by doxorubicin. A group of control mice were injected with saline.
The effects on tumour growth were assessed by measuring tumour volume before and after treatment.
Mice treated with doxorubicin followed with zoledronic acid were found to have almost complete elimination of breast tumour growth, 99.9 per cent.
But when the treatment order was reversed, or the drugs administered on their own, the treatment failed to reduce tumour volume compared with the control mice.
The researchers then examined sections of tumours removed from the successfully treated mice for markers of apoptosis.
They found that the treatment resulted in a 7.5-fold increase in the number of apoptotic cells within the tumours compared with tumours from the control mice. This suggests that the treatment reduces tumour volume by causing the cells to self-destruct.
What do the researchers say?
Lead researcher Professor Robert Coleman, from the University of Sheffield, said that the findings were 'very interesting but not yet fully understood'.
'The study shows that the schedule that the drugs are given in is very important.
'Breast cancer cells are sensitive to zoledronic acid but only after chemotherapy treatment.'
The zoledronic acid appears to reduce tumour volume by blocking angiogenesis, the process by which blood vessels are created to feed the tumour, and by inducing cell apoptosis, proposed Professor Coleman.
'We do not yet know how this treatment will relate to humans but we have recruited 3,400 patients for clinical trials and could have results as early as this December,' he added.
Dr Alexis Willett, policy manager at Breakthrough Breast Cancer, said: 'Breakthrough welcomes any research which investigates new uses for existing treatments to help benefit people with breast cancer.
'However, it's important to remember that this research is at a very early stage and further studies are needed before we will know whether this type of approach will be effective for women with breast cancer. We await further developments in this area with interest.'
What do other researchers say?
Dr Joanna Peak, science information officer at Cancer Research UK, said: 'Establishing the most effective combinations of drug treatments and the timings in which they are given is an important area of research.
But the benefits of giving zoledronic acid after doxorubicin have only been shown here in mice and now need to be evaluated more fully in people with breast cancer.'
- Treatment with doxorubicin followed by zoledronic acid can reduce breast tumour growth in mice.
- Treatment with the two drugs could offer the NHS a cheaper alternative to Herceptin.
- The treatment is currently being tested in human clinical trials.