乳房部分照射と従来の放射線療法の比較
（Abstract #: CRA532）

早期乳がんに対する乳房部分照射は従来の全乳房照射と同程度に有効である可能性がある

Partial breast irradiation may be as effective as traditional whole-breast radiation therapy for early-stage cancer

第45回American Society of Clinical Oncology学会で発表された3つの臨床試験のメタ解析の結果、早期乳がんに対する乳房部分照射は全生存率および転移の減少において従来の全乳房照射と有効性が同等である可能性が示された。研究者らは、乳房部分照射と従来の全乳房照射を比較した3つの臨床試験の対象となった女性1,140人のデータを評価した。全生存率および転移は二群間で有意差がなかった。しかし、乳房部分照射を受けた女性は原発巣の乳がんと同側の乳がん再発率が2倍であり、近傍の腋窩リンパ節のがん発現率が3倍であった。これらの再発は全生存率には影響しなかった。研究者らは、他の現在進行中の臨床試験の結果が解析されるまでは乳房部分照射は試験的治療と考えておくべきであると警告している。

A meta-analysis of data from three clinical trials shows that partial breast irradiation may offer the same benefits in terms of overall survival and reduction of metastases as conventional whole-breast radiation therapy for early-stage breast cancer. Investigators noted that several additional randomized studies are currently under way and no recommendations about this approach can be made until they are complete.

"Although more research is necessary, this study suggests that partial breast irradiation may be safe and feasible for women with early-stage breast cancer because it does not jeopardize patient survival or increase the risk of metastasis," explained lead author Antonis Valachis, M.D., associate breast cancer researcher at the Panhellenic Association for Continual Medical Research in Greece. "Partial breast irradiation reduces treatment time and radiation exposure to normal tissue, may improve cosmetic results, and is likely to enhance patients' ability to comply with therapy."

Conventional radiation therapy is commonly used to treat early-stage breast cancer after lumpectomy and it is typically given to the whole breast five days a week for six weeks. Partial breast irradiation, which was developed in the early 1990s, is targeted only to the breast tumor area. It may be given during surgery (either through radioactive seeds or through an inserted balloon catheter) with one application, or using targeted external three-dimensional conformal radiation therapy delivered over five to seven days after surgery is completed.

Dr. Valachis and his colleagues evaluated data on 1,140 women in three clinical trials comparing partial breast irradiation and traditional whole-breast radiation therapy. There were no significant differences in overall survival or the development of metastases between the two groups. However, women who received partial breast irradiation were twice as likely to experience cancer recurrence in the same breast as the primary tumor and three times more likely to develop cancer in the nearby axillary lymph nodes. These recurrences had no affect on overall survival, however.

The researchers cautioned that partial breast irradiation will continue to be considered investigational until the results of additional, ongoing clinical trials can be analyzed.