Preoperative magnetic resonance imaging may be a factor in the rising rate of mastectomy among women with early-stage breast cancer, a retrospective study suggests.
Investigators reviewed 5,596 stage 0-II breast cancers in 5,463 women who underwent surgery for the malignancy between 1997 and 2006 at the Mayo Clinic in Rochester, Minn. They found mastectomy rates decreased from 45% in 1997 to 30% in 2003, but then increased to 43% in 2006.
The rebound occurred in tandem with a doubling in the percentage of women who underwent preoperative breast MRI, lead study investigator Dr. Matthew Goetz noted in a preview of the findings during a press briefing conducted by the American Society of Clinical Oncology (ASCO).
The study's abstract was among thousands posted on the society's Web site in advance of its annual meeting. Under a new ASCO policy, only plenary and late-breaking abstracts have yet to be posted.
Dr. Goetz and his colleagues at the Mayo Clinic reported that 11% of women studied in 2003 underwent preoperative breast MRI, compared with 22% in 2006.
Patients who underwent preoperative breast MRI were significantly more likely to undergo mastectomy than were those who did not undergo preoperative breast MRI (52% vs. 38%). A similar increase in mastectomy rates was seen, however, in those who did not undergo preoperative MRI, with rates in those patients increasing from 28% in 2003 to 41% in 2006.
After adjustment for age, stage, contralateral breast cancer, and density, preoperative MRI was found to be an independent predictor of mastectomy (odds ratio 1.7, P less than .0001). Surgical year was also found to be a predictor of mastectomy. Compared with 2003, the odds ratios for mastectomy were 1.4 for 2004, 1.9 for 2005, and 1.7 for 2006 (P less than .0001).
Dr. Goetz noted that other factors might also play a role in the increasing number of women undergoing mastectomy. He cited patient preference—some women choose mastectomy over lumpectomy to maximize their risk reduction—and changes in medical procedures and technologies, such as improved breast reconstruction options and the introduction of genetic testing.
Dr. Julie Gralow, chair of the ASCO Cancer Communications Committee and moderator of the press briefing, added that studies have shown that when breast MRI is performed at the time of early-stage breast cancer diagnosis, more cancer is found in both the breast known to be affected and the contralateral breast than is found on mammography.
“It may be that these surgeries based on MRI are appropriate,” said Dr. Gralow of the University of Washington and the Fred Hutchinson Cancer Research Center, both in Seattle. MRI referral bias might also play a role in the increased mastectomy rates, she noted.
Additional study is required to further elucidate the influence of these various factors on surgical management, and to assess whether the changing trends in surgical management improve outcomes for women with breast cancer, Dr. Goetz said.
When breast MRI is performed at early-stage breast cancer diagnosis, more cancer is found than on mammography. DR. GRALOW