乳がんが転移すると生物学的特徴が変化する

肝臓に転移した乳がんは生物学的に変化し治療の有効性に影響を与える
Breast cancers that metastasize to the liver may change biology, impacting treatment effectiveness
転移性乳がんの女性に関するレトロスペクティブスタディの結果、原発腫瘍の生物学的特徴－エストロゲン、プロゲステロン、およびHER2の状態－が、がんが肝臓に転移した際にしばしば変化し治療法の変更が必要となることが示された。乳がん患者の治療法はキーとなる生物学的マーカー（エストロゲンおよびプロゲステロン受容体やHER2）の状態に基づき選択される。例えば、トラスツズマブはHER2を過剰発現する腫瘍にのみ有効であるが、タモキシフェンまたはアロマターゼ阻害薬はエストロゲン受容体陽性の患者にしか有効でない。しかし、医師は転移性腫瘍を毎回生検せず、原発性腫瘍の結果を参考に、時に何年も治療する。今回のスタディで研究者らは、転移性乳がん患者255人の原発乳がんおよび肝転移の生検データを調査し、エストロゲンおよびプロゲステロン受容体やHER2の状態を明らかにした。その結果、二次性腫瘍のエストロゲン受容体の状態は14.5%、プロゲステロン受容体の状態は48.6%、HER2の状態は13.9%において異なっていた。この結果から、12.1%の患者において治療法が異なってくる。このスタディは第46回ASCOで発表された。
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A retrospective study of women with metastatic breast cancer shows that the biological characteristics of their primary tumors - including estrogen, progesterone, and HER2 status - often changes when cancer spreads to the liver, requiring a change in therapy in more than 12 percent of patients.

"These results indicate that tumor biology often changes between primary and metastatic lesions, and suggest that biopsies of these secondary tumors should be performed whenever feasible," said co-author Giuseppe Curigliano, M.D., Ph.D., senior deputy director in the division of medical oncology at the European Institute of Oncology in Milan, Italy. "Traditionally, we start therapy according to the biological features of the primary tumor, and these results can influence treatment choices as many as 10 years later. Retesting secondary tumors will help us ensure that patients get the most effective therapy possible, which can have a dramatic impact on their overall outcome."

The choice of therapy for women with breast cancer is based on the status of key biological markers, such as estrogen and progesterone receptors and HER2. For example, trastuzumab (Herceptin) is only effective in women whose tumors overproduce HER2, while tamoxifen or aromatase inhibitors only work in breast cancer patients with estrogen receptor-positive tumors. But doctors don't routinely biopsy metastases, relying on the results of the primary tumor biopsy to guide treatment -- sometimes for many years.

In this study, researchers examined biopsy data from primary breast tumors and liver metastases in 255 women with metastatic breast cancer to determine the status of estrogen and progesterone receptors and HER2. They found changes in estrogen receptor status in the secondary tumor in 14.5 percent of women, progesterone status in 48.6 percent and HER2 status in 13.9 percent. This led to changes in therapy in 12.1 percent of the patients.