Oral Bisphosphonates May Significantly Reduce Breast Cancer

Results of a new analysis of data from the Women's Health Initiative (WHI) observational study showed that women who used bisphosphonates, which are commonly prescribed bone-strengthening pills, had significantly fewer invasive breast cancers than women who did not use bisphosphonates. These findings were presented at the CRTC-AACR San Antonio Breast Cancer Symposium.

In the 150,000-plus cohort of generally healthy postmenopausal women, the researchers found that women who used bisphosphonates, mostly alendronate, which is sold as Fosamax (alendronate sodium) by Merck, had 32% fewer cases of invasive breast cancer compared to women who did not use such drugs.

"The idea that bisphosphonates could reduce breast cancer incidence is very exciting because there are about 30 million prescriptions for these agents written annually in the United States targeting bone health, and more could easily be used to counteract both osteoporosis and breast cancer," said the study's lead investigator, Rowan Chlebowski, M.D., Ph.D., medical oncologist at the Los Angeles Biomedical Research Institute at Harbor-University of California, Los Angeles Medical Center.

The concept arose from findings in a report on an adjuvant breast cancer trial where use of the bisphosphonate zoledronic acid given intravenously every six months resulted in fewer contralateral breast cancers.

"It appeared to make bone less hospitable to breast cancer," Chlebowski said.

However, since bisphosphonates are prescribed for women with low bone mineral density and low bone mineral density has been associated with lower breast cancer incidence, a means to control for potential differences between women prescribed bisphosphonate and those not prescribed bisphosphonate in the cohort was needed.

Given that, Chlebowski and colleagues devised a way to control for use of bisphosphonates in the WHI. About 10,000 of the participants had bone mineral density analysis as part of the study, and for the rest they used a 10-item hip fracture predictive score to measure bone density. The researchers were able to correlate the findings from the women who had bone mineral density tests to findings from the predictive score in order to correct for any potential difference in bone density in women using bisphosphonates compared to non-users.

Studying 2,216 WHI participants who were using bisphosphonates when they entered the study, the researchers found that only 64 women developed breast cancer, and most of those cases (50) were estrogen receptor positive. Overall, there was a mean 32 percent fewer breast cancers in women using bisphosphonates compared to women who did not. There were 30 percent fewer estrogen receptor-positive cancers and 34 percent fewer entry receptor-negative cancers in bisphosphonate users. The latter finding was not statistically significant as there were very few receptor-negative cases.

"Bisphosphonates reduce angiogenesis and stimulate immune cells responsible for tumor cell surveillance as potential mediators," Chlebowski said. "This association needs to be studied further. While we currently have several options for reducing receptor-positive breast cancers, none are available for receptor-negative cancers."

Several ongoing adjuvant breast cancer trials evaluating oral and intravenous bisphosphonate will be available in the near future to provide randomized clinical trial evidence regarding their influence on new contralateral breast cancer risk, Chlebowski said.

For more information:

•  Onco'Zine - The International Cancer Network

Bisphosphonates and the Risk of Postmenopausal Breast Cancer

Bisphosphonates are routinely given to women with postmenopausal breast cancer, but new data suggest that these agents may play an important role in reducing recurrent breast cancer as well. Results of a new trial demonstrated that the use of bisphosphonates was associated with a 29% reduction in the risk of postmenopausal breast cancer. The results were presented at the CTRC-AACR San Antonio Breast Cancer Symposium.

Link between Bisphosphonates and Breast Cancer
When breast cancer metastasizes, it often spreads first to the bones. Bone metastases can lead to complications such as pain, fractures, spinal cord compression, bone marrow suppression, and hypercalcemia. The primary reason for this link is that breast cancer cells stimulate bone cells called osteoclasts, and these osteoclasts in turn stimulate the growth of breast cancer cells.

Bisphosphonates have emerged as a highly effective therapeutic option for the prevention of skeletal complications secondary to bone metastases. They interrupt the relationship between osteoclasts and breast cancer cells in early stage breast cancer, slowing the progression of bone metastases while, at the same time, reducing the skeletal complications in women with metastatic breast cancer. Research has also demonstrated that bisphosphonates may prevent the development of bone metastases in newly diagnosed patients with no evidence of metastasis.

A number of agents are now approved in both Europe and the US. They included Clodronate, Pamidronate, Ibandronate, Zoledronic acid.

New and ongoing research
Lead researcher Gad Rennert, M.D., Ph.D., chairman of the Department of Community Medicine and Epidemiology at the Carmel Medical Center of Clalit Health Services and a faculty member at the Technion-Israel Institute of Technology in Israel, said these data help shed light on a possible new pathway for breast cancer prevention.

"We have identified a new class of drugs that is associated with a reduced risk of breast cancer, and if proven in randomized trials, we may be able to recommend it to postmenopausal women for this purpose," said Rennert.

Rennert and colleagues extracted data from the Breast Cancer in Northern Israel Study, which is a population-based, case-control study. They evaluated the use of bisphosphonates for at least five years in 4,575 postmenopausal study participants using a structured interview. The self-reported, long-term use of bisphosphonates prior to diagnosis was associated with a significant reduced relative risk for breast cancer by approximately 34%.

This reduction remained significant, at 29%, even after adjusting for a large variety of risk factors for breast cancer such as age, fruit and vegetable consumption, sports activity, family history of breast cancer, ethnic group, body mass index, calcium supplement and hormone replacement therapy use, number of pregnancies, months of breastfeeding and age at first pregnancy.

Moreover, the breast tumors identified among patients who used bisphosphonates were more often estrogen receptor positive and less often poorly differentiated.

"These tumors are the type that are associated with a better prognosis," said Rennert.

While most experts are cautiously optimistic about the results of this study, several of them said that more information is necessary, and as of now, they would not suggest the use of bisphosphonates for women who do not have osteoporosis.

For more information:

• Coleman RE. Bisphosphonates in breast cancer. Ann Oncol 2005 May;16(5):687-95. Epub 2005 Mar 31.
• Logman JF, Heeg BM, Botteman MF, Kaura S, van Hout BA. Economic evaluation of zoledronic acid for the prevention of osteoporotic fractures in postmenopausal women with early-stage breast cancer receiving aromatase inhibitors in the UK. Ann Oncol. 2009 Dec 2. [Epub ahead of print]
• Ghazi M, Roux C. Hormonal deprivation therapy-induced osteoporosis in postmenopausal women with breast cancer. Best Pract Res Clin Rheumatol. 2009 Dec;23(6):805-11.
• Theriault RL. Bisphosphonates: ready for use as adjuvant therapy of breast cancer? Curr Opin Obstet Gynecol. 2009 Nov 19. [Epub ahead of print]

Also see:

• Onco'Zine - The International cancer Blog

Zoledronic Acid May Have Anti-Tumor Properties

Early evaluations of the bisphosphonate zoledronic acid (Zometa® , Novartis Oncology) suggest a possible direct anti-tumor effect when combined with neoadjuvant chemotherapy in breast cancer treatment, according to data presented to scientists and other medical professionals gathered at the Henry B. Gonzales Convention Center in San Antonio to hear and present the latest scientific findings in breast cancer research during the CTRC-AACR San Antonio Breast Cancer Symposium (December 10-14, 2008 ).

There is substantial in vitro evidence that zoledronic acid has direct antitumour effects and synergy with chemotherapy agents. Bisphosphonates may therefore be an adjuvant therapeutic strategy of potential importance.

‘Zoledronic acid is primarily targeted to bone and metastasis within the bone marrow microenvironment, but it may also be enhancing the response in the primary breast tumor,’ explained Robert Coleman, M.D., FRCP, professor of medical oncology at the University of Sheffield in the United Kingdom.

Coleman is the lead researcher on the AZURE (Adjuvant Zoledronic Acid to Reduce Recurrence) trial, a prospective, randomised, open label, parallel group trial designed to to evaluate the effect of zoledronic acid on breast cancer. ‘Although the larger AZURE trial is still being evaluated, if the findings in this smaller study are confirmed, the effect could be practice changing,' Coleman said.

The AZURE trial opened to recruitment in September 2003. Patients were recruited from 176 centres worldwide, completing accrual in January 2006, 8 months ahead of schedule, and enrolled 3,360 women with stage II/III breast cancer. The trial was set up to determine whether adjuvant treatment with 4 mg zoledronic acid in addition to adjuvant or neoadjuvant chemotherapy would improve the disease-free and bone metastasis-free survival of women with breast cancer at high risk of relapse.

Analysis of the characteristics of the study population shows that both groups are well
matched across all criteria. 51% of patients have T2 tumour at presentation, with 76.6% being ER positive. 60.6% and 33.2% had 1-3 and ≥4 axillary nodes involved respectively and 6.4% were treated in the neoadjuvant setting. Anthracyclines were administered to 92.6% and 22.7% received taxanes, in large part due to accrual into the TANGO trial concurrent with AZURE. Only 4.6% received endocrine therapy alone. Almost half of the patients (44.6%) were premenopausal at randomisation.

Coleman and colleagues performed a retrospective pathology analysis on 205 patients who received neoadjuvant chemotherapy to determine zoledronic acid’s impact on the primary tumor. Zoledronic acid appeared to reduce tumor size from 30 mm in the chemotherapy alone group to 20.5 mm in the combination group.

After adjusting for variables like estrogen receptor status and treatment duration, the difference remained at 42.4 mm in the chemotherapy group and 28.2 mm in the combination group. The pathological complete response rate was 5.8 percent in the chemotherapy arm and 10.9 percent in the zoledronic acid group.

The number of patients requiring mastectomy was 77.9 percent in the chemotherapy group and 65.3 percent in the combination group. ‘Zoledronic acid is currently approved for the treatment of bone metastasis and osteoporosis. If the AZURE trial remains positive, then we’ll file for an additional indication,’ Coleman said.

For more information, read:

• Winter MC, Thorpe HC, Burkinshaw R, Beevers SJ, Coleman RE. The addition of zoledronic acid to neoadjuvant chemotherapy may influence pathological response exploratory evidence for direct anti-tumor activity in breast cancer. Abstract 5101. Poster Session V: Treatment: Neoadjuvant Therapy. San Antonio Breast Cancer Symposium.

Also read:

• Click here for full prescribing information.
• The Institute of Cancer Research

Also read PubMed Abstracts:

• Lyseng-Williamson KA. Zoledronic Acid: a review of its use in breast cancer. Drugs. 2008;68(18):2661-82
• Brufsky A. Management of cancer-treatment-induced bone loss in postmenopausal women undergoing adjuvant breast cancer therapy: a Z-FAST update. Semin Oncol. 2006 Apr;33(2 Suppl 7):S13-7.