リンパ節への放射線照射は早期乳がんの予後を改善する（Abstract No. LBA1003）

局所リンパ節放射線照射を追加することにより早期乳がん女性の再発が減少する
Adding regional nodal irradiation decreases recurrences in women with early breast cancer
2011年ASCOで報告された無作為化Phase IIIトライアルの中間解析のデータから、リンパ節転移陽性または高リスクのリンパ節転移陰性乳がん患者において、局所リンパ節放射線照射（RNI）を併用することにより無病生存期間が改善し、腫瘍部位の近辺および他の身体部位のがん再発が減少することが報告された。このスタディは1,832人の女性を組み入れた。そのうちほとんど（85%）が1～3個のリンパ節転移を有しており、高リスクでリンパ節転移陰性の乳がんを有している割合（10%）は少なかった。全員が乳房温存術およびアジュバント化学療法または内分泌療法による治療を過去に受けており、その後、全乳房照射（WBI）単独またはWBIとRNI併用群に無作為に割り付けられた。フォローアップ期間中央値62ヵ月の後、RNIも受けた患者の無病生存率は33%改善した（WBI単独の84%からRNI併用療法89.7%、ハザード比0.67；p=0.003）。これには孤立性局所無病生存率の41%低下（5.5%から5年後3.2%、 p=0.02）、および遠隔無病生存率の36%低下（13%から5年後7.6%、p=0.002）が含まれた。全死亡率はRNI群において24%低下した（p=0.07）。
Full Text

Interim analysis data from a randomized Phase III trial reported at the American Society of Clinical Oncology's 47th Annual Meeting showed that, in women with node-positive or high-risk node-negative breast cancer, additional regional nodal irradiation (RNI), improves disease-free survival, reducing cancer recurrences both near the tumor site and in other parts of the body. In addition, overall mortality was reduced by 24 percent in the group receiving RNI, but this did not reach statistical significance.

"These results are potentially practice-changing. They will encourage physicians to offer all women with node-positive disease the option of receiving regional nodal irradiation," said Dr. Timothy J. Whelan, BM BCh, lead study investigator for the NCIC Clinical Trials Group and a professor of oncology and Division Head of Radiation Oncology at McMaster University and the Juravinski Cancer Centre, Hamilton, Ontario. "Adding regional nodal irradiation improved disease-free survival, lowered the risk of recurrences, and there was a positive trend toward improved overall survival, while not greatly increasing toxicities."

Women with node-positive breast cancer are treated with breast-conserving surgery plus axillary lymph node dissection, followed by whole breast irradiation (WBI). If a woman's cancer has high-risk features, such as a tumor larger than 5 cm or more than three positive axillary nodes, she often receives regional nodal irradiation, or RNI. However, for women with one to three positive nodes, the benefit of adding RNI has been unclear.

The study enrolled 1,832 women, most of whom (85 percent) had one to three positive lymph nodes, and a smaller proportion of women (10 percent) who had high-risk, node-negative breast cancer. All women had been treated with breast-conserving surgery and adjuvant chemotherapy or endocrine therapy. The participants were randomized to receive either WBI alone or WBI plus RNI.

A protocol specified interim analysis of the data conducted in March 2011 found that after a median follow up of 62 months, there were statistically significant benefits for the group receiving the added RNI therapy. These included a greater than 30 percent improvement in disease free survival (from 84 percent for those who received WBI to 89.7 percent for those who also got RNI at 5 years), as a result of a 41 percent lower rate of recurrences near the tumor site (from 5.5 percent to 3.2 percent at 5 years), and a 36 percent lower rate of cancer recurrences in other parts of the body (from 13 percent to 7.6 percent at 5 years).

The patients who received the added RNI had a low but statistically significant increased risk of grade 2 or greater pneumonitis and lymphedema.