Anastrozole與停經期之後的女性之骨折風險有關


  Sept. 23, 2003(哥本哈根)--一項大規模ATAC(Arimidex,它莫西芬單獨或組合治療)實驗的研究人員表示,用來治療早期乳癌的anastrozole與停經期之後的女性使用三到四年後的骨折風險有關。
  
  曼徹斯特大學的腫瘤學教授Anthony Howell博士表示,這項研究結果可以平息一些關於早期的疑問,也就是anastrozole會造成更多的骨折,Howell博士在第12屆歐洲癌症會議期間發表該研究結果,但anastrozole和它莫西芬在臀部骨折上並無差異,且六個月的骨折率仍相當穩定,anastrozole的骨折率可維持36個月,但是當解釋這些結果時,應該考慮它莫西芬的骨骼節約特性。
  
  就減少疾病復發率及較佳的安全條件而言,尤其是對於子宮癌和血栓性栓塞的事件,我們認為,anastrozole對於女性早期乳癌的整體風險與優點評估,仍然是有正向的意義。
  
  以前由實驗所發布的資料,包含21個國家共9,000名女性,顯示追蹤時間超過33個月之中,未患疾病的存活率為19%以上,服用anastrazole的患者,其對側乳房發生新腫瘤的比率比服用它莫西芬的患者低了58%,而更新的資料顯示,47個月的追蹤期間,服用anastrazole的組較佔優勢。
  
  對目前的分析而言,研究人員從六個月間,直到48個月的骨折發生率資料,來自ATAC研究的骨折發生率在治療後的每6個月進行評估,一直到48個月,分析包含anastrozole及它莫西芬之時間--骨折的模式。
  
  針對治療後31個月結果的第一次分析中顯示,服用anastrozole的骨折發生率為5.9%,而服用它莫西芬的骨折發生率則為3.7%,風險比率約為1.6,當更新37個月的安全資料時,骨折的風險及在二種藥物之間的差異,幾乎是一樣的。
  
  此外,臀骨骨折的風險,在這一批患者中是最令人擔憂的,這二組在統計上並無差異,脊椎骨和腕部colles骨的骨折風險在統計上也是相似的。
  
  但是anastrozole增加的骨折風險是否大到足以推翻它顯著的療效?以及推翻它相較於其他參數的安全性?德克薩斯大學乳癌研究中心的Debu Tripathy博士表示,短期資料顯示,服用anastrozole的疾病復發數字明顯地較低;這一點的絕對差異約為2.5%,當然,骨折差異也約為2%,但是骨折的結果和復發的結果是很一樣的。
  
  Tripathy博士表示,我認為最後哪種藥物得勝還很難說;我不認為你應該低估骨質疏鬆症方面的問題,因為這的確是長期的問題。
  
  Tripathy博士也指出,在ATAC實驗中的女性較不會因為乳癌而死亡,但是她們卻可能會發生骨質疏鬆症的併發症,因此,很難勸告女性,當你們70歲或80歲時,骨骼會變成什麼德性。
  
  荷蘭癌症研究院放射線治療科Harry Bartelink博士表示,你必須小心地觀察,且必須全面性地思考,老年女性的骨折風險當然較高,她們必須動手術,而可能發生手術的併發症,這是你必須認真治療的。
  
  另一方面,熟悉研究資料的Bartelink博士表示,利用微陣列進行簡單的遺傳測試,將有助於區別可以從anastrozole獲益最多的患者(例如患有腫瘤的女性之HER2為陽性的)以及辨別出可以受益於它莫西芬的患者。
  
  Bartelink博士說,在四或五年內,我們將可以選擇出最好的治療,而骨折也不再是個問題,因為那時候的患者存活率疾病的反應將更為進步。

Fracture Risk With Anastrozole

By Neil Osterweil
Medscape Medical News

Sept. 23, 2003 (Copenhagen) — The risk of bone fracture associated with the use of anastrozole for treatment of early breast cancer in postmenopausal women appears to reach a plateau and does not worsen after about three to four years, reported researchers from the large-scale ATAC (Arimidex, Tamoxifen Alone or in Combination) trial.

The finding should allay some concerns about the use of anastrozole for treatment of early breast cancer in older women, according to Anthony Howell, MD, professor of oncology at the University of Manchester and a medical oncologist at the Christie Hospital in Manchester, U.K.

"There's no doubt that there are more fractures with anastrozole," said Dr. Howell at a media briefing held here during the 12th annual European Cancer Conference. "But there's no difference between anastrozole and tamoxifen for hip fractures, and the six-month fracture rate remains relatively stable in both groups, with anastrozole stabilizing after 36 months, and the bone-sparing properties of tamoxifen should be taken into account when you interpret these results. In view of the reduction in disease recurrence and the favorable safety profile with other things as far as anastrozole is concerned — especially in endometrial cancer and thromboembolic events are concerned — our view is that the overall risk benefit ratio for anastrozole for women with early breast cancer remains positive."

Previously released data from the trial, involving more than 9,000 women in 21 countries, showed that over a median follow-up of 33 months, disease-free survival was 19% better, and the incidence of new tumors in the contralateral breast was 58% less with anastrazole than with tamoxifen. An update of the data at a median of 47 months showed an absolute difference in favor of anastrozole.

For the current analysis, the researchers looked at data on fracture incidence at six-month intervals for up to 48 months of treatment. Fracture incidence from the ATAC study was assessed every six months up to 48 months of treatment. The analysis included differences in patterns of time-to-fracture for anastrozole vs. tamoxifen.

In the first analysis of results from 31 months of therapy, the fracture incidence was 5.9% in women taking anastrozole and 3.7% for those receiving tamoxifen, a risk ratio of about 1.6. When an update of safety data was performed at 37 months, the risk of fractures, and the difference between the two drugs, was about the same, Dr. Howell said.

In addition, the risk of hip fracture, one of the most important concerns in this group of patients, was not statistically different between the two groups. The risk of spine and wrist/colles fractures were also statistically similar, according to Dr. Howell.

But is the increased risk of fracture with anastrozole great enough to mitigate against its use given its apparently superior efficacy and favorable safety profile in other parameters?

"The short-term data show the number of recurrences [with anastrozole] is clearly lower; the absolute difference at this point is about 2.5%," said Debu Tripathy, MD, professor of medicine and director of the breast cancer research center at the University of Texas Southwestern Medical Center, in Dallas, who commented on the study in an interview with Medscape. "Of course, the fracture difference is also about 2%, but the consequences of a fracture and the consequences of a recurrence are very different."

Dr. Tripathy concluded, "I think in the end which one wins out long term is going to be difficult to say; I don't think you should underestimate the problem with osteoporosis, though, because that is really a long-term issue."

Dr. Tripathy noted that the women in the ATAC trial were less at risk to die from breast cancer than from other causes, and they could be subject to late complications of osteoporosis. "So this is a very tricky issue trying to counsel women now when we don't have data 20 years down the line what are your bones going to look like when you're 70, 80 years old."

"You have to look carefully, but you have to look at the total picture," said Harry Bartelink, MD, chairman of radiotherapy at the Netherlands Cancer Institute in Amsterdam, in an interview with Medscape. "The risk of fractures is, of course, that it happens to older women, and they have to be operated on and you have complications from the surgery, so that's something you have to take seriously."

On the other hand, said Dr. Bartelink, who is familiar with the study data, the advent of relatively simple genetic testing with microarrays can help to differentiate between patients who might benefit most from anastrozole (such as women with tumors that are positive for HER2) and those who may benefit from tamoxifen. "In four or five years we will be able to select which is the best treatment and then the bone fractures are not a problem anymore, because then the gain in survival and disease response is much larger," Dr. Bartelink told Medscape.

ECCO 12: Abstract 676. Presented Sept. 24, 2003.

Reviewed by Gary D. Vogin, MD

    
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