早期乳がんの高齢女性は放射線療法を見合わせても安全である

乳腺腫瘍摘出術を施行された高齢のstage I乳がん患者に対して放射線療法は不要な可能性がある

Radiation may not be needed by older women with stage 1 breast cancer who have had a lumpectomy

ある追跡調査の結果、乳腺腫瘍摘出術を施行されタモキシフェンを投与された70歳以上の早期乳がん女性に対しては、放射線療法を行わなくとも生存率に有意に影響しない可能性があるとのエビデンスがさらに得られたと第46回ASCOで発表された。研究者らは、エストロゲン受容体陽性のリンパ節転移のないstage I乳がんに対し乳腺腫瘍摘出術を施行された70歳以上の女性636人を、タモキシフェン投与群（319人）またはタモキシフェンと放射線療法（317人）併用群に無作為に割り付けた。早期解析の結果、フォローアップ期間中央値7.9年後にタモキシフェン単独治療はタモキシフェンと放射線療法併用治療と有効性が同等であることが示された。この新たな解析には10.5年後の追跡データも含まれた。同側乳房の乳がん再発リスクはタモキシフェンと放射線療法併用群においてタモキシフェン単独療法群よりも低かった（それぞれ2%と8%）。しかし、乳がん特異的生存率は両群間で有意差がなかった。10年後の乳がん生存率はタモキシフェン単独群で98%であり併用群で96%であった。タモキシフェン単独群の10年生存率は63%であったのに対しタモキシフェン放射線療法併用群では61%であった。

A follow-up study adds further evidence that women age 70 or older with early-stage breast cancer who undergo lumpectomy and receive tamoxifen may safely forego radiation therapy without significantly affecting their survival.

"The standard of care for women 70 and older with very small tumors that are estrogen-positive and node-negative - the largest group of breast cancer patients in this age group - had been lumpectomy and radiation," said lead author Kevin Hughes, M.D., surgical director, breast screening, and co-director of the Avon Comprehensive Breast Evaluation Center at the Massachusetts General Hospital in Boston. "Earlier reports of this study with shorter median follow-up have shown the risk of recurrence without radiation to be only marginally worse than with radiation, but there was concern that longer follow-up would show a blossoming of recurrences. This study confirms that for older women with early-stage breast cancer, lumpectomy without radiation is a viable alternative, and tamoxifen may replace the need for radiation."

Radiation therapy after lumpectomy is the standard of care for younger women with early-stage breast cancer. Dr. Hughes and his colleagues looked at whether this therapy is also appropriate for older women, who often have less aggressive disease and are less likely to experience a recurrence.

The researchers randomly assigned 636 women aged 70 or older with stage I, estrogen receptor-positive, node-negative breast cancer who had a lumpectomy to receive tamoxifen (319 women) or tamoxifen and radiation (317 women). An earlier analysis by these investigators showed that after a median follow-up of 7.9 years, tamoxifen alone was an effective alternative to tamoxifen and radiation. This new analysis includes follow-up data after 10.5 years.

The risk of breast cancer recurrence in the same breast was lower among the women who received tamoxifen plus radiation therapy (2 percent) compared with those who received tamoxifen alone (8 percent). However, there were no significant differences between the two groups with respect to breast cancer-specific and overall survival: After 10 years, breast cancer-specific survival for women who received tamoxifen was 98 percent versus 96 percent for those who received tamoxifen and radiation. The tamoxifen-only group had a 10-year overall survival of 63 percent compared to 61 percent to the tamoxifen plus radiation group.

This study was presented at ASCO's 46th Annual Meeting in Chicago.

Disclosures: Nothing to disclose.