微小転移乳がんの治療（Abstract #: CRA596）

A group of Dutch researchers has found that women with early-stage breast cancer who have micrometastases in the sentinel lymph node have a significantly higher rate of recurrence if they do not receive follow-up treatment on additional axillary lymph nodes. They also report that about one in ten doctors are not treating these very small metastases.

For patients with early-stage breast cancer, physicians examine the sentinel lymph node to determine the extent that cancer has spread and whether additional treatment is needed in the remaining axillary lymph nodes. Treatment generally involves a second operation to remove the axillary lymph nodes, but radiation therapy is also used. For macrometastases- metastases greater than 2.0 mm - evidence of the need for further treatment has been clear.

Evidence has been less certain, however, for patients with micrometastases - metastases between 0.2 mm and 2.0 mm, and for patients with isolated tumor cells (individual cells or tumor cell clusters smaller than 0.2 mm).

"We found that about 10 percent of doctors are not treating micrometastases. This is most likely due to concern about overtreatment and a lack of clear data on these very small metastases, but our study provides explicit evidence that foregoing treatment for micrometastases results in high cancer recurrence rates. We hope these findings will be a tipping point for doctors not currently treating women for this stage of cancer," said Vivianne Tjan-Heijnen, M.D., Ph.D., a professor of medical oncology at the Maastricht University Medical Center in the Netherlands and the study's lead author. "Additionally, our study suggests that radiation therapy is a good alternative to surgery, which could spare many women additional recovery, although more data to confirm these findings are warranted."

This retrospective study included about 2,700 women who underwent surgery for early-stage breast cancer between 1997 and 2005 and had a sentinel node biopsy that showed no evidence of macrometastases. Women were then divided into three groups: Those with no tumor cells in the sentinel node, those with isolated tumor cells, and those with micrometastases. All women either underwent no additional treatment, surgery to remove remaining axillary nodes, or radiation therapy to the axillary nodes.

For patients with micrometastases, the five-year recurrence rate in the axillary nodes was 4.5 times higher for patients who had no additional treatment than for patients who had either surgery or radiation. Additional axillary treatment did not significantly improve recurrence rates among women with either no tumor cells or only isolated tumor cells in the sentinel node.