Study: Tumor size does not affect prognosis in basal breast cancers

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A study published in the Nov. 1 issue of Cancer found that the long-term prognosis for women with basal breast cancer with large tumors was similar for women presenting with small tumors; however, women with large basal tumors appear to develop recurrent disease more quickly.

According to Rebecca Dent, MD, and colleagues from the department of medical oncology at Odette Cancer Center, Sunnybrook Health Sciences Center and the University of Toronto, basal-like breast cancer is a subgroup of breast cancers that are known for having an unusually aggressive course. This subgroup of cancer is marked by the lack of staining for estrogen-receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER-2/neu). It is also defined by positive staining for the cytokeratins (CKs) expressed in the myoepithelial cells of the ducts and lobules (CK5/CK6, CK14) and for epidermal growth factor receptor (EGFR).

It is uncertain whether or not traditional prognosis factors for breast cancer could also predict the outcome for patients with basal-like cancers and, according to the authors, the purpose of the study was to determine time-to-disease recurrence in the case of basal-type breast cancers.

The study stained a panel of 962 breast cancers for five markers (ER, PR, HER-2/neu, CK5/CK6 and EGFR). The patients involved in the investigation were followed for up to 15 years from diagnosis for clinical outcomes. Rates of distant disease recurrence and death were compared by tumor size (2 cm or more than 2 cm) and the status of the lymph nodes were taken into consideration in both groups of women presenting with basal and nonbasal cancers.

The researchers determined that 116 of the 962 cases of cancer were basal (12 percent). They found 88 percent were nonbasal and one case was excluded from the study because it could not be determined positively whether it was basal or nonbasal.  

Dent and colleagues also reported that 426 tumors measured greater than 2 cm (45 percent) and 530 tumors measured less than 2 cm (55 percent).

The findings showed that after 10 years, mortality rates were equal for both women with large tumors and women with small tumors. However, it was noted that large tumor size within women with nonbasal cancers was found to be an unfavorable prognostic factor and only a transient adverse effect of size on disease recurrence was distinguished in women with basal cancers.