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Updated results from a large breast cancer prevention trial confirm that both the old standby tamoxifen and the osteoporosis drug Evista can substantially cut the risk of developing breast cancer in high-risk postmenopausal women.

 

April 20, 2010 (Washington, D.C.) -- There are two good drug options for preventing breast cancer in high-risk women, and more women need to take advantage of them, doctors say.

Updated results from a large breast cancer prevention trial confirm that both the old standby tamoxifen and the osteoporosis drug Evista can substantially cut the risk of developing breast cancer in high-risk postmenopausal women.

Tamoxifen works a little better, but Evista may be a little safer, says study head D. Lawrence Wickerham, MD, of Allegheny General Hospital in Pittsburgh.

But "only 5% to 20% of the tens of thousands of women" who could benefit from the drugs use them, says Gabriel Hortobagyi, MD, a breast cancer specialist at the University of Texas M.D. Anderson Cancer Center in Houston who was not involved with the work.

Over 192,000 women, about 150,000 of whom were postmenopausal, were diagnosed with breast cancer in 2009, he says.

Updated results from the STAR (Study of Tamoxifen and Raloxifene ) trial were presented at the annual meeting of the American Association for Cancer Research and published online by the journal Cancer Prevention Research.

Tamoxifen has been used for years to help fight breast cancer's return. In 1998, the FDA approved tamoxifen for use by women who hadn't had breast cancer but were at high risk of developing the disease.

Evista, known generically as raloxifene, is taken by about half a million women in the U.S. to prevent and treat osteoporosis, or thinning of the bones. In 2007, the FDA approved it for breast cancer prevention in some high-risk postmenopausal women based on earlier results from STAR and other trials.

As a breast cancer preventive, they're recommended for women at higher-than-average risk because of genetic mutations, family history, or other factors, including age over 60.

 

Tamoxifen vs. Evista

 

The updated analysis of the federally funded study involved nearly 20,000 postmenopausal women followed for almost seven years during and after treatment with either tamoxifen or Evista.

Earlier findings from the study, published in 2006, showed that both drugs reduced the risk of breast cancer by about 50% in high-risk, postmenopausal women. But Evista appeared to carry fewer risks of side effects, with lower rates of uterine cancer and clotting problems.

The new findings suggest that several years after treatment, which lasts about five years, tamoxifen is substantially better than raloxifene at preventing breast cancer.

About two years after treatment ended, tamoxifen reduced the risk of invasive breast cancer by 50%, while Evista cut risks by 38%.

Put another way, Evista was 76% as effective as tamoxifen, says Wickerham, who serves as a consultant to makers of both drugs.

Evista was about 78% as effective as tamoxifen at preventing noninvasive breast cancers (lobular carcinoma in situ and ductal carcinoma in situ).

But women who took Evista "continued to have substantially fewer of the serious side effects, including uterine cancers, clotting problems, and cataracts , that seem to be barriers to tamoxifen use," he says.

There were 2.25 cases of uterine cancer per 1,000 women treated with tamoxifen vs. 1.23 per 1,000 among women treated with Evista. There were 3.30 blood clot events per 1,000 women treated with tamoxifen vs. 2.47 per 1,000 among women treated with Evista.

"The absolute risk of these problems for any given woman is quite low, regardless of treatment," says M.D. Anderson's Scott Lippman, MD.

There was no difference in death rates among the two groups. Neither of the drugs has been shown to extend lives in high-risk women.

 

Who Is Considered a High-Risk Patient?

 

So which drug is better for which women? Both drugs are only for women at high risk, doctors stress .

In the study, women were considered to be at high risk if their risk of developing breast cancer over the next five years was 1.67% based on a simple formula called the Gail model that takes into account age, family history, and other factors. By definition, anyone over age 60 was at high risk.

But Hortobagyi says he probably wouldn't give the drugs to a woman in her 60s who is otherwise healthy based on age alone. "It's a discussion each woman needs to have with her doctor. The more risk factors, the greater she will benefit."

If you and your doctor conclude you are at increased risk and you are not at risk for blood clots or uterine cancer, both drugs are good breast cancer prevention options, Hortobagyi says. If you are at risk for these problems, Evista is the better choice, he says.

All things being equal, some women may want to take tamoxifen because it is slightly more effective, the experts say.

On the other hand, postmenopausal women with thinning bones might want to consider Evista because it "offers two benefits in one," Lippman says.

The study only included postmenopausal women, but as a treatment for breast cancer, tamoxifen has a proven track record in premenopausal women as well, Hortobagyi says. Evista is only approved for use after menopause, so its safety and effectiveness in premenopausal women is unknown, he says.

High-risk premenopausal women who have had a hysterectomy -- and therefore a "close to nonexistent" risk of uterine cancer -- and who have no history of blood clots may want to talk to their doctor about taking tamoxifen, he says.

Both drugs cost about $140 a month or $8,400 for five years of treatment. In comparison, treating one case of early breast cancer can easily cost $50,000 to $120,000, according to Hortobagyi.

 

WebMD Health News
by Charlene Laino
Reviewed By Laura Martin
Last Modified: 2010/4/20 下午 04:07:15 c 2010 WebMD, LLC. All rights reserved.

 

研究顯示,Tamoxifen效果好一點,但Evista可能風險較少。

  【24drs.com】April 20, 2010(華盛頓特區)-- 醫生們表示,高風險婦女可選擇兩種很好的藥物來預防乳腺癌,而且有更多婦女需要服用這兩種藥物。
  
  有個大型的乳腺癌預防試驗結果證實,無論是之前的替代藥物tamoxifen,還是骨質疏鬆症藥物Evista,都可以顯著降低高風險停經後婦女罹患乳腺癌的風險。
  
  匹茲堡Allegheny綜合醫院的Lawrence Wickerham醫師表示,Tamoxifen的效果稍微好一點,但Evista可能比較安全一點。
  
  未參與這項研究的休士頓德州大學安德森癌症中心乳癌專家Hortobagyi醫師表示,數萬名婦女中,只有5%至20%可以因為服用該藥物而受益。
  
  他表示,2009年被診斷患有乳腺癌的19萬2千多名婦女中,大約有15萬人已過更年期。
  
  STAR(Tamoxifen和Raloxifene的研究)試驗所更新的結果將在美國癌症研究協會的年會中發表,並刊載在癌症預防研究(Cancer Prevention Research)期刊的網路版上。
  
  用Tamoxifen來對抗乳腺癌復發已經很多年了,美國食品藥品管理局(FDA)在1998年核准沒有乳腺癌但卻是高風險的婦女使用tamoxifen。
  
  美國大約有50萬名婦女服用Evista(raloxifene),來預防和治療骨質疏鬆症或是骨頭變薄。FDA依據STAR和其他試驗的初步結果,在2007年核准某些高風險的停經後婦女用來預防乳腺癌。
  
  這兩種藥物用於預防乳腺癌時,是建議給因為基因突變、有家族史、或其他因素,包括超過60歲,而使風險高於平均的婦女服用。
  
  【Tamoxifen與Evista】
  聯邦政府贊助的這篇研究最新分析,是針對近2萬名停經後婦女在用tamoxifen或Evista治療期間和治療後追蹤約7年。
  
  2006年所發表的這篇研究初步結果顯示,這兩種藥物能降低高風險、停經後婦女罹患乳腺癌約50%的風險,但Evista的副作用風 險較少,子宮內膜癌和凝血問題的比例較低。
  
  這篇最新研究結果顯示,持續治療大約5年後,tamoxifen預防乳腺癌的效果明顯優於raloxifene。在結束治療後大約2年,tamoxifen降低50%侵入性乳腺癌的風險;Evista減少38%的風險。
  
  這兩種藥物製造商的顧問Wickerham醫師表示,換句話說,Evista比tamoxifen的效果好76%。
  
  Evista在防止非侵入性乳腺癌(乳小葉原位癌和乳管原位癌)的效果是tamoxifen的78%。
  
  但他表示,服用Evista的婦女其嚴重副作用持續大幅減少,包括子宮內膜癌、凝血問題、以及白內障等,這些似乎是服用tamoxifen的障礙。
  
  每1千名用tamoxifen治療的婦女中,有2.25個子宮癌的案例;每1千名用Evista治療的婦女中,有1.23個案例。每1千名用tamoxifen治療的婦女中,有3. 30個凝血問題案例;每1千名用Evista 治療的婦女中,有2.47個案例。
  
  安德森癌症研究中心的Scott Lippman醫師表示,不論用什麼方式治療,這些問題對任何特定婦女的絕對風險都是相當低的。
  
  兩組的死亡率沒有差異,都沒有顯示出可以延長高風險婦女的生命。
  
  【誰被認定是高風險患者?】
  因此,哪種藥對哪些婦女較好?醫生強調,這兩種藥物都只適用於高風險婦女。
  
  在這篇研究中,被認為是高風險的婦女在未來5年內會罹患乳腺癌的風險是1.67%,這是根據所謂Gail model的簡單公式計算出來的結果,該公式有考量年齡、家族史、以及其他因素。根據定義,所有60歲以上的人都是高風險族群。
  
  但是Hortobagyi醫師表示,他可能不會開藥給只有年齡符合,但其他方面是健康的60多歲婦女。每一個婦女都需要與醫生討論。風險因素越多,受益會越多。
  
  Hortobagyi醫師表示,如果你和醫生確認你的風險在增加,而且沒有血塊或子宮內膜癌的風險,那這兩種藥物都是預防乳腺癌很好的選項。他表示,如果有這些風險,那Evista會是較好的選擇。
  
  專家們表示,假如所有條件都相同,那有些婦女可能會想要服用tamoxifen,因為它比較有效。
  
  Lippman醫師表示,另一方面,停經後的婦女骨頭較薄,可能要考慮Evista,因為它可提供兩種益處。
  
  Hortobagyi醫師表示,這項研究只有針對停經後婦女,但tamoxifen作為乳腺癌的治療時,對停經前婦女也有良好的記錄。他表示,Evista只核准在停經後使用,因此,他們不知道對停經前的婦女來說,它的安全性和有效性如何。
  
  他表示,沒有凝血病史的婦女,以及做過子宮切除術的高風險停經前婦女--因為「幾乎不會有」子宮內膜癌風險,可能會想與醫生討論服用tamoxifen。
  
  Hortobagyi醫師表示,這兩種藥物的費用大約是每個月140美元,或是5年的治療期共8,400元。相較之下,治療1個初期乳腺癌很容易就要花費5萬至12萬美元。


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