Mastectomy Rates Decreasing in US, Nationwide Stats Show

Zosia Chustecka

June 24, 2010

June 24, 2010 — Mastectomy rates are decreasing in the United States, concludes a new study of nationwide statistics published online June 14 in the Journal of Clinical Oncology.

In contrast to widely publicized findings from several single-institution studies that have reported increasing rates of mastectomy in recent years, the new study found that, nationwide, mastectomy rates have in fact been decreasing.

Using data from the Surveillance, Epidemiology, and End Results (SEER) database, the researchers identified 233,754 patients who had been diagnosed with breast cancer (ductal carcinoma in situ or stage I to III unilateral breast cancer).

The proportion of women who underwent a mastectomy fell significantly, from 40.8% in 2000 to 37% in 2006 (P < .001).

"Our results show that, on a national basis, mastectomy use has decreased," conclude Elizabeth Habermann and colleagues from the University of Minnesota in Minneapolis.

Although there are some limitations to the information that is stored in the SEER database (e.g., there were no details on family history, genetic testing results, or chemotherapy use), the researchers emphasize that this is a "robust population database and accurately reflects cancer treatment trends" in the United States.

Contrast With Previous Findings

Dr. Habermann and colleagues note that their nationwide findings are in contrast to those from 3 single-institution studies that have recently reported significantly increased rates of mastectomy, and which have "naturally . . . generated considerable media coverage and speculation."

Those single-institution studies reported the following increases in mastectomy rates:

  • from 35% in 2004 to 60% in 2007 at the H. Lee Moffitt Cancer Center in Tampa, Florida (from a review of 5865 patients)

  • from 28% in 1998 to 30% during the 2003 to 2008 period at the Magee-Women's Hospital in the University of Pittsburg in Pennsylvania (from a review of 3606 patients)

  • from 31% in 2003 to 43% in 2006 at the Mayo Clinic in Rochester, Minnesota (5405 patients).

This study from the Mayo Clinic was highlighted at a press briefing at the 2008 annual meeting of the American Society of Clinical Oncology and later published in the Journal of Clinical Oncology with an accompanying editorial, as reported at the time by Medscape Oncology.

The difference between findings from these single-institution studies and our larger nationwide study might be explained by variations in referral patterns and patient selection, Dr. Habermann and colleagues write. Patients themselves might elect to go to larger institutions for aggressive surgery, such as a mastectomy, and physicians might be more likely to refer patients with a strong family history or documented BRCA gene mutation to a large institution. The single-institution studies might also reflect practice patterns within particular geographic regions, they note, adding that their nationwide study did find geographic differences.

"I do believe that our study gives a better picture of the use of mastectomy across the United States than the single-institution studies," Dr. Habermann told Medscape Oncology. "Women who visit the Mayo Clinic or the Moffitt Cancer Center for the treatment of their breast cancer may be different from the average American woman," she added.

However, the authors point out that they "cannot exclude the possibility that national trends may trail the findings reported from single-institutional studies, and that mastectomy rates in the [United States] may increase in the future." They note that they did see an increase in the last 2 years of their study; "patients diagnosed in the year 2006 were slightly more likely to undergo mastectomy than those diagnosed in 2005."

"It is surely possible that the single-institution reports come from places that are ahead of the nationwide trend, meaning that we may see mastectomy rates increase nationwide later than when our data ended (in 2006)," Dr. Habermann said.

Increase in Contralateral Prophylactic Mastectomy

Although the new study found that total mastectomy and unilateral mastectomy rates decreased over time, it also showed that the rate of bilateral mastectomy (including contralateral prophylactic mastectomy [CPM]) increased significantly, from 2.5% in 2000 to 5.7% in 2006.

The authors previously reported on this significant increase in CPM rate (J Clin Oncol. 2009;27:1362-1367), and now they note that the increase is continuing through 2006 without a plateau.

Other studies have also reported an increase in the rate of CPM, they add.

The reasons for this observed increase in CPM are not clear, but contributing factors might include increased awareness of genetic breast cancer, improved mastectomy and reconstruction techniques, increased use of breast magnetic resonance imaging (MRI), and changing perceptions of the importance of breast-conserving treatment, they note.

"I am not a surgeon and I do not see patients, so I am hesitant to offer a reason as to why women are choosing CPM," Dr. Habermann told Medscape Oncology. "It is likely that increased genetic testing is one reason, as well as more stories about CPM in the mass media increasing awareness that CPM is a choice for women."

Might Be a "True Trend"

Approached for independent comment, Jennifer Obel, MD, attending physician at NorthShore University Health System in Evanston, Illinois, and a breast cancer expert at the American Society of Clinical Oncology, said: "I do agree with the authors' perspective."

"There is inherent bias in a single-institution study," Dr. Obel said. "Patients who travel to academic centers, like the Mayo Clinic and Moffitt Cancer Center, are different from those patients who receive care closer to home. The mere act of traveling to a tertiary-care center makes this patient population unique. We know that patients who receive care at academic centers tend to have more complicated cases. These patients may be younger and they may have a significant family history, which impacts decision making regarding surgical approach. "

When the increase in mastectomies was reported in previous studies, it was suggested that it might have resulted from an increase in the use of MRI for breast cancer. However, Dr. Obel pointed out that "if the increase in mastectomy rates was solely attributed to newer imaging modalities (like MRI, which increases detection of occult disease), we would have seen an increase not only in contralateral mastectomy (bilateral mastectomy), but there would also have been an increased rate of unilateral mastectomy. That is not the case in the SEER data. In fact, the authors found an increase rate of contralateral mastectomy, likely owing to imaging, but decreased use of unilateral mastectomy."

Hence, she said, "the true trend across the country may be one of decreased use of mastectomy, not the trend that has been reported in isolated centers."

The authors have disclosed no relevant financial relationships.

J Clin Oncol. Published online June 14, 2010. Abstract


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