Letrozole能增進Tamoxifen 治療後的無病存活率


  Oct. 10, 2003--根據一項先前發表於10月9日線上新英格蘭醫學期刊(New England Journal of Medicine)的研究結果顯示,經Tamoxifen治療五年後,以芳香酵素抑制劑 letrozole治療,可以明顯增進罹患初期乳癌的停經婦女的無病存活率,這項研究將出現在11月6日的期刊標題。
  
  由於letrozole治療組與安慰劑組相比所得到的存活優勢,使得這項設計用來試驗tamoxifen治療後給予letrozole治療五年的研究,追蹤期的中位數僅為2.4年即被中斷。
  
  根據加拿大安大略多倫多瑪格麗特公主醫院血液及腫瘤學部門的Paul E. Goss博士及其同事表示,tamoxifen對於雌激素受體既是拮抗劑又是協同劑,隨著時間,它的協同作用可能變得過度因此削減了它的潛在拮抗作用,相較之下,letrozole抑制了雌激素生成和改進tamoxifen中斷後的結果。
  
  因此,研究人員在一項雙盲,randomized 試驗中,對於5,187位因荷爾蒙-陽性乳癌而接受至少5年tamoxifen治療的女性給予每日2.5mg的letrozole或安慰劑以進行評估。
  
  在追蹤期中位數2.4年後,letrozole治療組有75位局部或轉移性乳癌復發或新發癌症於對側乳房,接受安慰劑治療組則有132位。估計四年無病存活率在letrozole治療組及安慰劑治療組分別為93%和87%(P P = .25)。
  
  Goss博士及其同事指出,低度的熱潮紅、關節炎、關節痛、肌肉痛在letrozole治療組較為頻繁,但是陰道出血症狀的頻率減少,雖然兩組的骨折發生率類似,將其骨質疏鬆的發生率相比,安慰劑治療組發生率為4.5%,letrozole治療組的發生率為5.8%。
  
  美國賓夕法尼亞州匹茲堡大學撰寫社論的John Bryant博士及匹茲堡Allegheny 省立醫院Norman Wolmark博士提到,無病存活利益的重要性在於其顯著且著名的tamoxifen持續性效果。
  
  他們也指出服用過量letrozole對於有心血管疾病的婦女可能產生潛在令人擔憂的長期效應,他們建議,若能與盲樣安慰劑治療組做比對,長期追蹤婦女數年以上,有其重要的價值。
  
  第二作者,美國麻薩諸塞州波士頓哈佛醫學院Likewise博士評論指出,有人認為以letrozole治療2或3年已被評估,也有人認為這項治療最理想的期間仍未確立。
  

Letrozole Improves Disease-Fre

By Emma Hitt, PhD
Medscape Medical News

Oct. 10, 2003 — Treatment with the aromatase inhibitor letrozole after five years of tamoxifen treatment appears to improve disease-free survival in postmenopausal women with primary breast cancer, according to the results of a study released early online Oct. 9 in the New England Journal of Medicine. The study will appear in the Nov. 6 print issue of the journal.

The study, designed to test five years of letrozole treatment after tamoxifen therapy, was discontinued after a median follow-up of only 2.4 years due to the survival benefit observed in the letrozole group compared with the placebo group.

According to Paul E. Goss, MD, PhD, from the Division of Hematology and Oncology at the Princess Margaret Hospital in Toronto, Ontario, Canada, and colleagues, tamoxifen is both an antagonist and a partial agonist of the estrogen receptor. "Over time, its agonist action may become exaggerated and thereby impair its potential anticancer activity," they note. In contrast, letrozole suppresses estrogen production and could improve outcome after discontinuation of tamoxifen.

Therefore, the researchers evaluated letrozole 2.5 mg daily or placebo in a double-blind, randomized trial of 5,187 women with hormone-positive breast cancer who had completed at least five years of tamoxifen therapy.

After a median follow-up of 2.4 years, 75 local or metastatic recurrences of breast cancer or new cancers in the contralateral breast were noted in the letrozole group compared with 132 in the placebo group. The estimated four-year disease-free survival rates were 93% and 87% in the letrozole and placebo groups, respectively (P P = .25).

"Low-grade hot flashes, arthritis, arthralgia, and myalgia were more frequent in the letrozole group, but vaginal bleeding was less frequent," Dr. Goss and colleagues point out. In addition, incidence of osteoporosis was 5.8% in the letrozole group compared with 4.5% in the placebo group (P = .07), although the rates of fracture were similar between the two groups. The magnitude of disease-free survival benefit "is remarkable, given the well-known carryover effect of tamoxifen," note editorialists John Bryant, PhD, from the University of Pittsburgh, Pennsylvania, and Norman Wolmark, MD, from Allegheny General Hospital, Pittsburgh, Pennsylvania.

However, they point out that a "potentially disquieting long-term effect is the possible excess in cardiovascular events among women taking letrozole." They suggest that "it would have been of great value to have been able to follow the women over a period of years in comparison with a blinded placebo group."

Likewise, in a second editorial, Harold J. Burstein, MD, PhD, from Harvard Medical School in Boston, Massachusetts, comments that "one can say only that letrozole treatment for a period of two to three years has been evaluated and that the optimal duration of such therapy has not been established."

The authors report that they have received research support from Novartis, the manufacturer of letrozole.

N Engl J Med. Published online Oct. 9, 2003. Reviewed by Gary D. Vogin, MD

    
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