ゾレドロン酸の乳がんに対する有効性が確認された（Abstract # S1-2）

ABCSG-12：閉経前ER陽性乳がん女性の生存におけるゾレドロン酸の長期有益性が示された
ABCSG-12: Zoledronic acid shows long-term benefit in survivorship for premenopausal ER-positive breast cancer
エストロゲン受容体陽性の閉経前乳がん患者を、卵巣機能抑制を含むアジュバント内分泌治療に加えアジュバントゾレドロン酸により治療することの持続的な有効性が証明された。オーストラリア乳がん＆大腸がんスタディグループ（Austrian Breast & Colorectal Cancer Study Group[ABCSG-12]）のデータが2011年CTRC-AACRサンアントニオ乳がんシンポジウムで報告され、過去に報告されたデータが確認および追加された。現在フォローアップ84ヵ月の時点で、毒性副作用はなく患者らの乳がん再発は劇的に減少し生存率は改善した。研究者らはこの4群トライアルにおいて、早期のエストロゲン受容体（ER）陽性乳がんの閉経後女性1,803人を、タモキシフェンまたはアナストロゾールまたは各々とゾレドロン酸を3年間投与される群に無作為に割り付けた。治療の84ヵ月後に、ゾレドロン酸投与群において再発率は28%低下し死亡リスクは36%低下した。また、想定完全卵巣遮断療法を受けた40歳以上の患者では再発リスクが34%低下し死亡リスクは44%低下した。40歳未満の女性においては生存に関する有意な利益は認められなかった。下顎骨壊死や腎不全の発現はみられなかった。
Full Text

Researchers have proven the continuing effectiveness of treating patients with estrogen receptor-positive premenopausal breast cancer with adjuvant zoledronic acid in addition to adjuvant endocrine treatment including ovarian function suppression.

Data from the Austrian Breast & Colorectal Cancer Study Group (ABCSG-12), reported at the 2011 CTRC-AACR San Antonio Breast Cancer Symposium, held Dec. 6-10, 2011, confirmed and extended data reported at 48 months and 62 months of follow-up. Now at 84 months of follow-up, patients are experiencing drastically fewer recurrences of breast cancer and improved rates of survivorship without toxic side effects.

"We have confirmed what this trial showed initially, which was both exciting and surprising," said Michael Gnant, M.D., professor of surgery and president of the ABCSG at the Medical University of Vienna. "The continued success of this treatment means we can intervene early and still observe persistence of the benefit of treatment."

In the four-arm trial, researchers randomly assigned 1,803 premenopausal patients with early-stage, estrogen receptor (ER)-positive breast cancer to receive tamoxifen or anastrazole or each of these two treatments with zoledronic acid for three years. In the initial report, presented in 2008, Gnant and his colleagues reported significantly improved disease-free survival.

The most recent long-term data, at 84 months after treatment, revealed a 28 percent reduced risk for recurrence and a 36 percent reduction in risk for death among patients treated with zoledronic acid. Also, no patients experienced osteonecrosis of the jaw or renal failure ― thus, Gnant said, proving the safety of the treatment seven years later.

Researchers also found that patients aged older than 40 years with presumed complete ovarian blockade had a 34 percent reduced risk for recurrence and a 44 percent reduced risk for death. They found no significant survival benefits among patients aged younger than 40 years.

Gnant and his team said these data, considered with previously demonstrated bone-protective effects of zoledronic acid, suggest that adding zoledronic acid to adjuvant endocrine therapy including ovarian function suppression should be considered for premenopausal women with ER-positive early breast cancer.