使用Anastrozole五年會促進骨質疏鬆病程


  June 12, 2006 (亞特蘭大) — 根據研究者在此間舉行的第42屆美國臨床腫瘤學會年會中所報告,乳癌女性用aromatase抑制劑anastrozole (Arimidex, AstraZeneca) 治療五年會降低6%到7%的骨密度(BMD),足以造成那些原本骨質缺乏者變成骨質疏鬆症。
  
  主要研究者Robert E. Coleman醫師表示,然而,對於原本BMD正常的婦女,服用anastrozole 5年不會導致骨質疏鬆症;他發表的是比較Arimidex、Tamoxifen單獨或者併用(ATAC)利益的研究發現;Coleman醫師是英國Sheffield大學腫瘤科教授。
  
  研究中發現,服用anastrozole的婦女約40%會增加骨折風險,當停藥後,這些骨折風險就降低。
  
  ATAC試驗收納有侵入性第一級乳癌之停經後婦女,將她們隨機分組接受Arimidex或 tamoxifen治療或併用治療;根據以前的試驗結果,Arimidex於預防乳癌復發方面優於tamoxifen或併用療法。
  
  此一68個月的次組分析,比較了81位以Arimidex治療的婦女和86位以tamoxifen治療的婦女;於開始時、第一年、第二年和第五年,利用雙能量X光骨密度檢查測量腰椎BMD和整體BMD;第五年時,服用anastrozole的婦女損失了髖部 6.1% 、脊柱7.2%的 BMD;tamoxifen組損失了髖部2.8%、脊柱0.7%的 BMD (P < 0.0001)。
  
  研究中服用tamoxifen者的整體骨折率是7.7%,服用anastrozole者的整體骨折率是11%;雖然Coleman醫師強調這兩者之差異是顯著的,但是他的報告中沒有提到P 值,他指出,那是因為服用anastrozole和服用tamoxifen者的髖骨骨折率沒有統計上的顯著差異。
  
  流失率經時遞減;第二到第五年的流失率顯著比前兩年減少 (平均年度改變率差異為 0.0113; 95% CI, 0.006 – 0.0017; P = 0.0002)。
  
  一開始是骨質缺乏的5名病患,在追蹤期結束時發展成骨質疏鬆症。
  
  基於前述結果,Coleman醫師建議服用anastrozole的婦女要每一到兩年檢查其BMD,她們在服用anastrozole期間應該也要服用鈣片和維他命D。
  
  未參與研究的Stephen Y. Chui 醫師指出,這結果是有趣的,原本正常BMD者不會發展成骨質疏鬆症,這發現對使用aromatase抑制劑治療的前五年是可靠的,但我們不知道五年後的有關骨骼健康的長期風險;但是,此有關aromatase抑制劑對原本正常 BMD之婦女的安全性的觀察還是可靠的;Chui 醫師是奧勒岡健康科學大學助理醫學教授、乳癌臨床資訊主治醫師。
  
  若採我們的新療法,可以有更多的乳癌存活者,這些病患原為正常BMD者就不需要如前述所建議之定期監測BMD 。
  
  有一建議指出,對病患使用aromatase抑制劑併雙磷酸鹽,但這或許無助於降低風險因子;這些發現幫助我們預判何者需要介入治療、何者不需要。

Five Years on Anastrozole Can<

By Paula Moyer, MA
Medscape Medical News

June 12, 2006 (Atlanta) — Women with breast cancer who are treated with the aromatase inhibitor anastrozole (Arimidex, AstraZeneca) for 5 years can lose 6% to 7% in bone-mineral density (BMD), enough to trigger a progression to osteoporosis in those who are already osteopenic when treatment begins, according to a group of investigators that reported these findings here at the 42nd annual meeting of the American Society of Clinical Oncology.

For women with normal BMD at baseline, however, taking anastrozole for 5 years is unlikely to cause osteoporosis, said principal investigator Robert E. Coleman, MD, in a briefing. He presented these findings on behalf of the Arimidex, Tamoxifen, Alone or in Combination (ATAC) trial investigators. Dr. Coleman is a professor of oncology at the University of Sheffield in the United Kingdom.

Women taking anastrozole also had about a 40% increased risk of fractures while on the study, he said, adding, "When the drug was discontinued, the excess fracture risk declined."

The ATAC trial recruited postmenopausal women with invasive primary breast cancer and randomized them to receive adjuvant treatment with Arimidex, tamoxifen, or combination therapy. According to previously reported trial results, Arimidex was superior to tamoxifen or combination therapy for preventing recurrence of breast cancer.

This 68-month subset analysis compared BMD between 81 women treated with Arimidex and 86 women treated with tamoxifen. Lumbar spine and total hip BMD were measured by dual-energy x-ray absorptiometry at baseline, 1 year, 2 years, and 5 years. At 5 years, women taking anastrozole lost 6.1% of BMD at the hip and 7.2% at the spine vs losses of 2.8% at the hip and 0.7% at the spine in the tamoxifen group (P < 0.0001).

The overall fracture rate was 7.7% among women taking tamoxifen in the study vs 11% for women taking anastrozole. Although Dr. Coleman stressed that the difference was significant, he did not report the P value. There was, he said, no statistically significant difference in the rate of hip fractures between women taking anastrozole and those taking tamoxifen.

The rate of loss decelerates over time; the rate at 2 to 5 years was significantly less than the loss over the first 2 years of treatment (mean difference in annual rate of change, 0.0113; 95% CI, 0.006 – 0.0017; P = 0.0002).

Five patients with osteopenia at baseline developed osteoporosis by the end of the follow-up period, he said.

On the basis of these results, Dr. Coleman recommended that women taking anastrozole have their BMD monitored every 1 to 2 years. "They should also take calcium and vitamin D supplements during anastrozole therapy," he said.

"It was interesting that women with a normal BMD at baseline did not develop osteoporosis," said Stephen Y. Chui, MD, who was not involved in the study. "This finding is reassuring for the first 5 years after a woman starts aromatase-inhibitor therapy, but we don't know what the long-term risks to bone health are after 5 years. Nonetheless, this observation regarding the safety of an aromatase inhibitor in women with normal baseline BMD is reassuring." Dr. Chui is an assistant professor of medicine at Oregon Health Sciences University in Portland, where he is an attending physician in the multidisciplinary breast cancer clinic.

"With our newer therapies, we will have more breast cancer survivors," he said. "These patients with normal baseline BMD may not require BMD monitoring as frequently as the annual recommendation. 

"There have been suggestions to start an aromatase inhibitor patient on bisphosphonates. Maybe that's not appropriate with lower risk factors. These findings may help us predict who needs intervention and who doesn't."

ASCO 42nd Annual Meeting: Abstract 511. Presented June 4, 2006.


    
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