Triple-Negative Breast Tumors Impact Poor, Black, and Hispanic

SACRAMENTO, Calif., March 29 -- So-called triple-negative breast cancers -- tumors that do not express the major prognostic markers -- are particularly aggressive, according to researchers here.

An analysis of the California Cancer Registry database also shows that regardless of the stage at diagnosis, prognosis for triple-negative tumors is worse than for other breast cancers at a comparable stage, according to Katrina Bauer of the Public Health Institute here.

The analysis also shows that women with triple-negative breast tumors tend to be younger, poorer, and to be either Hispanic or black, the investigators reported online today in advance of the May 1, 2007, issue of Cancer.

The phenotype of the triple-negative tumor lacks the estrogen (ER), progesterone (PR), and HER2 receptors, and is usually classified as basal-like, the researchers noted. This finding has an intuitive inconsistency because HER2-positive tumors are highly aggressive in and of themselves. But the lack of HER2 positivity apparently does not outweigh the negativity of both ER and PR receptors, the investigators said.

Because such malignancies do not respond to any of the endocrine treatments currently available, there is interest in finding other targeted therapies and treatment strategies.

Also, little had been known about demographic factors associated with the triple-negative cancers. To fill that gap, the researchers looked at 92,358 women with first primary breast cancer diagnosed between 1999 and 2003 whose records were included in the California Cancer Registry.

Of those, the status of all three markers was known in 51,074 women, of whom one in eight (6,370, or 12.5%) was missing all three, the researchers found.

The researcher performed multivariate analysis comparing the two groups for such things as age, race or ethnicity and stage at diagnosis. A broader analysis, comparing the triple-negatives to all other women in the cohort, gave similar results and details were not presented.

The analysis found women with triple-negative breast cancers were:

• More likely to be under age 40, with 12.2% versus 5.7% for other cancers, which was significant at P<0.001. The odds ratio was 1.53, with a 95% confidence interval from 1.37 to 1.70.
• Significantly more likely to be non-Hispanic black, at P<0.001. The odds ratio was 1.77, with a 95% confidence interval from 1.59 to 1.97.
• Significantly more likely to be Hispanic, at P<0.001. The odds ratio was 1.23, with a 95% confidence interval from 1.14 to 1.34.

Triple negative cancers were significantly more likely (P<0.001) to be diagnosed among women who lived in low-income areas, the researchers also found, using U.S. census data.

Triple-negative patients typically were diagnosed at a later stage. For instance, nearly half of the women with other breast cancers (45.7%) presented at Stage I, compared with 32.8% of the triple-negative women, a difference that was significant at P<0.001.

At the same time, significantly more women presented at Stage III and IV (P=0.001 and P<0.001, respectively).

The median tumor size for the triple-negative group was 22 mm, compared with 17 mm among the other women, a difference that was significant at P <0.001).

Also, 76% of triple-negative breast tumors were classified as poorly differentiated or undifferentiated, compared with 28% of the other tumors, a difference significant at P <0.001.

Relative survival for women with triple-negative breast cancer was poorer than for women with other types of breast cancer -- 77% of triple-negative women surviving five years after diagnosis, compared with 93% for other women.

The study has several limitations, the researchers said: It is a population-based cancer registry investigation, histologic grading of tumors and tests for the prognostic markers were performed without central review, almost half the initial study population lacked information about all of the markers, and there were no microarray or immunohistochemistry assays to confirm the connection to the basal-like tumor subtype.