MR features help radiologists identify triple-negative breast cancer

Mar 9, 2009

Triple-negative (TN) breast cancer, in which the tumor is estrogen receptor negative, progesterone receptor negative, and human epidermal growth factor receptor 2 (HER2) negative, tends to be harder to diagnose, giving these women fewer treatment options and worse prognoses than those with non-TN tumors. Because of this, researchers are investigating whether TN breast cancer has any clinical markers that can be used to recognize it.

Dr. Takayoshi Uematsu, Ph.D., and colleagues at Shizuoka Cancer Center Hospital in Nagaizumi, Japan, conducted a study to determine specifically if certain MR characteristics can help radiologists identify triple-negative breast cancer. Their findings are published in this month's issue of Radiology (March 2009, Vol. 250:3, pp. 638-647).

"Triple-negative breast cancer can mimic benign breast lesions, making it difficult for mammography or ultrasound to distinguish it," Uematsu told AuntMinnie.com via e-mail. "But breast MRI can reveal the cancer's intratumoral characteristics, such as necrosis and fibrosis."

The study included 176 women with surgically confirmed TN breast cancer; the mean age of the group was 56 years. MR exams were performed with a 1.5-tesla MR unit (Gyroscan Intera, Philips Healthcare, Andover, MA) with breast surface coils. Two radiologists with eight and 12 years of breast MR imaging experience read the images without knowing the surgical findings. Triple-negative breast cancer characteristics were compared to those of breast cancers that were estrogen receptor positive, progesterone receptor positive, and HER2 negative.

Women with triple-negative breast cancer were more likely to have histologically high-grade tumors and unifocal lesions than those who did not have it (86% versus 13.7% and 66% versus 46.2%, respectively).

Characteristics of patients with triple-negative breast cancer and those with ER-positive/PR-positive/HER2-negative breast cancer

	Characteristic	Triple-negative cancer (n = 59)	ER-positive/ PR-positive/ HER2-negative cancer (n = 117)	P value

	Age (y)*	60 (30-87)	56 (29-83)	0.253

	Tumor size (mm)*	21 (7-55)	19 (10-70)	0.139

	Histologic tumor grade			< 0.001

	Low	0 (0)	23 (19.7)

	Moderate	8 (14)	78 (66.7)

	High	51 (86)	16 (13.7)

	Histologic tumor type

	Invasive ductal carcinoma	44 (75)	98 (83.8)	0.145

	Invasive lobular carcinoma	4 (7)	11 (9.4)	0.776

	Medullary carcinoma	7 (12)	1 (0.9)	0.002

	Metaplastic carcinoma	4 (7)	0 (0)	0.012

	Mucinous carcinoma	0 (0)	7 (6.0)	0.097

	Axillary lymph node positivity	21 (36)	45 (38.5)	0.711

	Unifocal lesion	39 (66)	54 (46.2)	0.012

Note: Unless otherwise indicated, data are numbers of patients, with percentages in parentheses. Percentages may not add up to 100% because of rounding. *Data are means, with ranges in parentheses. All data courtesy of the Radiological Society of North America.

As for lesion type, 95% of triple-negative breast cancer lesions showed as masses on MR, compared with 66.7% of non-TN cancers. Furthermore, the researchers found that triple-negative breast cancer lesions tended to show smooth mass margin, rim enhancement, persistent enhancement pattern, and very high intratumoral signal intensity on T2-weighted MR images.

Comparison of MR imaging findings in mass lesion types between patients with triple-negative breast cancer and patients with ER-positive/PR-positive/HER2-negative breast cancer

	MRI imaging finding	Triple-negative cancer (n = 56)	ER-positive/ PR-positive/ HER2-negative cancer (n = 78)	P value

	Mass shape			0.065

	Round	10 (18)	11 (14)

	Oval	13 (23)	30 (38)

	Lobulated	23 (41)	12 (15)

	Irregular	10 (18)	25 (32)

	Mass margin			0.001

	Smooth	22 (39)	11 (14)

	Irregular	34 (61)	67 (86)

	Internal enhancement			< 0.001

	Homogeneous	0 (0)	2 (3)

	Heterogeneous	11 (20)	76 (97)

	Rim enhancement	45 (80)	0 (0)

	Intratumoral signal intensity on T2-weighted images			0.002

	Low or equal	30 (54)	66 (85)

	High	7 (12)	3 (4)

	Very high	19 (34)	9 (12)*

	Pattern at dynamic enhancement imaging			0.005

	Persistent	24 (43)	16 (21)

	Plateau	4 (7)	37 (47)

	Washout	28 (50)	25 (32)

Note: Numbers in parentheses are percentages. Percentages may not add up to 100% because of rounding. *Of these nine lesions, seven were mucinous carcinomas. All data courtesy of the Radiological Society of North America.

One of the surprising findings in the study was the time-signal intensity curve pattern of triple-negative breast cancer, Uematsu told AuntMinnie.com.

"Initially, rapid enhancement and a washout pattern is generally regarded to be a malignant pattern on breast MR imaging," he wrote in an e-mail. "However, this doesn't apply to triple-negative breast cancers. This different enhancement pattern may come from the heterogeneity of the triple-negative breast cancer."

Another surprising finding? Dynamic contrast-enhanced breast MR imaging with T2-weighted images works to identify this type of cancer, according to Uematsu. Of course, tissue samples are still important.

"This technique can increase the specificity of breast MR imaging because of correlation of intratumoral necrosis with the hyperintense area on T2-weighted images," he wrote. "But breast MR imaging with imperfect positive predictive values and negative predictive values cannot replace tissue samples."

By Kate Madden Yee
AuntMinnie.com staff writer
March 10, 2009

Triple-negative breast cancers more likely to affect young, poor minority women, April 13, 2007

Prognostic markers in triple-negative breast cancer identified, February 15, 2007

Protein could help detect aggressive breast cancer, January 26, 2007