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Aromatase Inhibitors: Bone Effects Can Be Serious
Tue Jun 13, 8:00 PM ET
Aromatase inhibitors can cause significant bone loss over the long term, according to new research presented in Atlanta at the annual meeting of the American Society of Clinical Oncology.
Although researchers have known that this new class of hormone therapy for breast cancer is harder on bones than tamoxifen, the new results are helping them understand how serious the differences are -- and will lead to ways to better manage this side effect.
The new findings come from a large international clinical trial known as ATAC (Arimidex and Tamoxifen, Alone or in Combination), which in 2004 showed that the aromatase inhibitor Arimidex (anastrozole) was better than tamoxifen at preventing breast cancer recurrences in women past menopause. The current study involved about 300 women from the original trial.
The researchers measured bone density in the women on both drugs at the beginning of the trial and after 5 years of hormone therapy. They found that women in the tamoxifen group had slightly improved bone density.
But women in the Arimidex group had about 6% reduced bone density in the lower back (lumbar spine) and about 7% reduced bone density in the hip. Normal bone loss for women in this age group over this period of time is only about 2%-3%, said lead study author Robert Coleman, MD, professor of medical oncology at Weston Park Hospital in Sheffield, England.
Strong Bones Resist Damage Better
But not all women on Arimidex suffered the same amount of bone loss. About 15% of women whose bones were normal at the study's start still had normal bone density after 5 years of treatment, and none developed osteoporosis. All the women who did develop osteoporosis while on Arimidex had weakened bones to begin with, Coleman said.
This information is helpful for doctors planning follow-up for women on Arimidex, Coleman said. Patients who are at risk of bone loss should be monitored for it every couple of years, and can be advised to exercise and take calcium and vitamin D supplements. Some women may need to be treated with bisphosphonates.
Although the information revealed in this study is not surprising, it is important, said Len Lichtenfeld, MD, deputy chief medical officer for the American Cancer Society.
"We need to bear in mind that this is a side effect that can have serious consequences," he said. "Hip fractures can be deadly, especially in older women."
Vitamin D May be Key
A second study presented at Saturday's conference suggests that how much vitamin D a woman has in her body when she starts taking an aromatase inhibitor may influence how serious her bone loss will be. This research involved a different aromatase inhibitor, Aromasin, (exemestane).
Women in the study had all had surgery for early breast cancer and then were randomly assigned to take Aromasin or a placebo. As expected, women on Aromasin had higher levels of bone loss. But the researchers were surprised to see that even women on placebo had high levels of bone loss.
The team suspected vitamin D might be the cause, said study leader Per Lonning, MD, PhD, professor of medical oncology and radiation oncology at Norway's Bergen University.
"Vitamin D status is a potential risk factor for bone loss," he explained.
When Lonning and colleagues measured blood levels of vitamin D, they found something Lonning calls "quite provocative."
Among women with low levels of vitamin D, there was a significant difference in bone loss between the Aromasin group and the placebo group. But there was no such difference when the women had sufficient vitamin D in their blood.
That suggests vitamin D levels are playing some role in the bone loss associated with aromatase inhibitors, Lonning said.
"We can't make a final conclusion from this paper, but it's important to study further," he said.
Citations: "Effect of anastrozole on bone mineral density: 5-year results from the 'Arimidex,' Tamoxifen, Alone or in Combination (ATAC) trial." Abstract #511, presented June 4, 2006, at the annual meeting of ASCO. First author: Robert E. Coleman, MD, Weston Park Hospital, Sheffield, UK.
"Vitamin D deficiency: A threat to bone health in breast cancer patients during adjuvant treatment with aromatase inhibitors." Abstract #554, presented June 3, 2006, at the annual meeting of ASCO. First author: Per Lonning, MD, PhD, Haukeland University Hospital, Bergen, Norway.
Tue Jun 13, 8:00 PM ET
Aromatase inhibitors can cause significant bone loss over the long term, according to new research presented in Atlanta at the annual meeting of the American Society of Clinical Oncology.
Although researchers have known that this new class of hormone therapy for breast cancer is harder on bones than tamoxifen, the new results are helping them understand how serious the differences are -- and will lead to ways to better manage this side effect.
The new findings come from a large international clinical trial known as ATAC (Arimidex and Tamoxifen, Alone or in Combination), which in 2004 showed that the aromatase inhibitor Arimidex (anastrozole) was better than tamoxifen at preventing breast cancer recurrences in women past menopause. The current study involved about 300 women from the original trial.
The researchers measured bone density in the women on both drugs at the beginning of the trial and after 5 years of hormone therapy. They found that women in the tamoxifen group had slightly improved bone density.
But women in the Arimidex group had about 6% reduced bone density in the lower back (lumbar spine) and about 7% reduced bone density in the hip. Normal bone loss for women in this age group over this period of time is only about 2%-3%, said lead study author Robert Coleman, MD, professor of medical oncology at Weston Park Hospital in Sheffield, England.
Strong Bones Resist Damage Better
But not all women on Arimidex suffered the same amount of bone loss. About 15% of women whose bones were normal at the study's start still had normal bone density after 5 years of treatment, and none developed osteoporosis. All the women who did develop osteoporosis while on Arimidex had weakened bones to begin with, Coleman said.
This information is helpful for doctors planning follow-up for women on Arimidex, Coleman said. Patients who are at risk of bone loss should be monitored for it every couple of years, and can be advised to exercise and take calcium and vitamin D supplements. Some women may need to be treated with bisphosphonates.
Although the information revealed in this study is not surprising, it is important, said Len Lichtenfeld, MD, deputy chief medical officer for the American Cancer Society.
"We need to bear in mind that this is a side effect that can have serious consequences," he said. "Hip fractures can be deadly, especially in older women."
Vitamin D May be Key
A second study presented at Saturday's conference suggests that how much vitamin D a woman has in her body when she starts taking an aromatase inhibitor may influence how serious her bone loss will be. This research involved a different aromatase inhibitor, Aromasin, (exemestane).
Women in the study had all had surgery for early breast cancer and then were randomly assigned to take Aromasin or a placebo. As expected, women on Aromasin had higher levels of bone loss. But the researchers were surprised to see that even women on placebo had high levels of bone loss.
The team suspected vitamin D might be the cause, said study leader Per Lonning, MD, PhD, professor of medical oncology and radiation oncology at Norway's Bergen University.
"Vitamin D status is a potential risk factor for bone loss," he explained.
When Lonning and colleagues measured blood levels of vitamin D, they found something Lonning calls "quite provocative."
Among women with low levels of vitamin D, there was a significant difference in bone loss between the Aromasin group and the placebo group. But there was no such difference when the women had sufficient vitamin D in their blood.
That suggests vitamin D levels are playing some role in the bone loss associated with aromatase inhibitors, Lonning said.
"We can't make a final conclusion from this paper, but it's important to study further," he said.
Citations: "Effect of anastrozole on bone mineral density: 5-year results from the 'Arimidex,' Tamoxifen, Alone or in Combination (ATAC) trial." Abstract #511, presented June 4, 2006, at the annual meeting of ASCO. First author: Robert E. Coleman, MD, Weston Park Hospital, Sheffield, UK.
"Vitamin D deficiency: A threat to bone health in breast cancer patients during adjuvant treatment with aromatase inhibitors." Abstract #554, presented June 3, 2006, at the annual meeting of ASCO. First author: Per Lonning, MD, PhD, Haukeland University Hospital, Bergen, Norway.
