乳房切除術施行の傾向（Abstract #: 509）

The increase in mastectomies documented among women with early-stage breast cancer at one major medical center may be partially related to greater use of preoperative magnetic resonance imaging, according to a presentation at the annual meeting of the American Society of Clinical Oncology.

Researchers at the Mayo Clinic (Rochester, Minnesota) reported that the number of mastectomies performed at their institution increased 13 percent from 2003 to 2006:? Mastectomy accounted for 43 percent of procedures for early-stage breast cancer in 2006 compared with 30 percent of procedures in 2003.

The study also found that women who underwent preoperative breast magnetic resonance imaging were significantly more likely to undergo mastectomy than those who did not, although the rise in mastectomy rates was observed in both groups.

Preoperative breast examination with magnetic resonance imaging (MRI) may find cancer in more than one part of the breast, which may lead physicians and patients to choose mastectomy more often than lumpectomy. About half of the lesions detected by MRI are benign and only need to be monitored, but some women with such lesions may still choose mastectomy because they feel anxious or do not want to undergo periodic breast biopsies.

"This study demonstrates that a significant number of women with early-stage breast cancer are undergoing mastectomy, and it appears to be partially related to the introduction of pre-operative MRI," said Rajini Katipamula, MD, senior clinical fellow in hematology/oncology at Mayo Clinic and the study's lead author.

Breast-conserving surgery (lumpectomy) plus radiation therapy has been the treatment of choice for most American women with early-stage disease since 1990, when a National Institutes of Health Consensus Panel reported that it was as effective as mastectomy for overall survival for most women with stage I and II breast cancer.

Shortly thereafter, mastectomy rates began to decline. But in recent years, surgeons have performed more mastectomies, prompting Mayo Clinic researchers to conduct this retrospective study.

The researchers evaluated mastectomy trends in relation to surgical year and use of preoperative breast MRI using findings from a database of breast data started at the institution in 2003 among 5,464 women who had surgery for early-stage breast cancer at the Mayo Clinic between 1997 and 2006.

Mastectomy rates had declined from 45 percent in 1997 to 30 percent in 2003, but then rose to 43 percent in 2006. The percentage of women who had breast MRI doubled from 11 percent in 2003 to 22 percent in 2006. More than half (52 percent) of the patients receiving MRI underwent mastectomy compared with 38 percent of the patients who did not have MRI.

Additionally, the study showed that mastectomy rates increased in women who did not undergo MRI, from 28 percent in 2003 to 41 percent in 2006.