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Researchers Identify Characteristics and Treatment of Metaplastic Breast Cancer: Presented at SSO

By Ted Bosworth

SAN DIEGO, C.A. -- March 29, 2006 -- An analysis of the natural history of metaplastic breast cancer has reinforced previous assertions that this is a unique form of breast cancer that may deserve a unique management strategy.

In a study that compared data on 892 metaplastic breast cancers to those collected on 255,164 infiltrating ductal carcinomas (IDC) of the breast, one of the most important conclusions drawn from the data is that metaplastic breast cancer appears to grow at a relatively rapid rate.

"The metaplastic cancers seem to be larger at the time of detection and behave differently biologically," reported Christopher M. Pezzi, MD, surgical oncologist, Department of Surgery, Abington Memorial Hospital, Abington, Pennsylvania.

Speaking here on March 26^th at the annual meeting of the Society of Surgical Oncology (SSO), Dr. Pezzi noted that the number of reports of metaplastic breast cancers has been growing since 2001, when a separate code first recognized this malignancy as a distinct entity.

Although these cancers represent only 0.3% of all breast malignancies, the reported cases increased by 38% between 2001 (243 cases) and 2003 (331 cases), most likely as a result of increased recognition, he said.

Dr. Pezzi and colleagues screened data from the National Cancer Database for all metaplastic breast cancers and IDCs over a 2-year period. A large variety of factors were compared in the two groups, including patient age and ethnicity, tumor size, nodal status, cancer stage, cancer grade, cancer hormone receptor status, and treatment.

A large number of significant differences between the two groups were identified, although many were of uncertain clinical significance, he said.

Patients with metaplastic cancer were on average 1.5 years older than IDC patients (61.1 vs. 59.7; P <.001) and were more likely to be African-American (14.1% vs. 10.2%; P =.001). However, metaplastic cancer patients were more likely to have tumors that were larger than 2 cm in diameter (>70% vs. <50%; P <.001) and were more likely to have poorly differentiated or undifferentiated malignancy (>65% vs. <40%; P <.001). They were far less likely to have estrogen receptor positive tumors (8.1% vs. 53.7%; P <.001).

Treatment was generally more aggressive in the metaplastic patient group. This appeared to reflect physician concerns about poor differentiation.

Patients with metaplastic cancer -- although they were more likely to be node negative (80.2% vs. 66.8%) -- were less likely to receive breast conserving therapy (28.5% vs. 55.8%; P<.001) and more likely to receive chemotherapy (53.4% vs. 42.1%; P<.001).

However, the therapeutic decisions were similar when such factors as tumor size and histology were considered.

"Right now, the data suggest that physicians are managing metaplastic breast cancer on the basis of decisions extrapolated from other types of breast cancer. This is really all that can be done because of the minimal amount of data specific to metaplastic cancers available, but it is not clear that this will prove to be the best approach," Dr. Pezzi said.

He noted that several studies of metaplastic breast cancer are now underway, and suggested "that we should have more data with which to consider these malignancies in 1 to 2 years."


[Presentation title: Characteristics and Treatment of Metaplastic Breast Cancer: Analysis of 892 Cases from the National Cancer Database. Abstract 82]

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