In a 2001 study published in the Proceedings of the National Academy of Sciences, further stratified the classifications described by Perou et al. and explored the clinical value of these breast cancer subtypes. The authors separated the ER-positive tumors into two distinct groups and found that tumor classification based on gene expression was related to patient survival. The expression of 427 genes was measured for 78 cancers and seven non-malignant breast samples. Following hierarchical clustering, the samples formed two groups at the highest level of organization reflecting the ER-positive and ER-negative phenotypes; the ER-negative cluster further stratified to groups identical to those described. In contrast to previous results, found that the ER-positive group could also be separated into three distinct subgroups termed luminal subtypes A, B, and, C based on patterns of luminal-specific gene expression with different outcomes. The authors further found once they performed survival analyses that tumors belonging to the various groups showed significantly different outcomes when treated uniformly. Survival analyses are often shown as Kaplan-Meier survival plots, an example of which is shown to the right.

In addition to identifying genes that correlate to survival, microarray analyses have been utilized to establish gene expression profiles associated with prognosis. It is agreed upon that patients with tumors exhibiting poor prognostic features would benefit the most from adjuvant therapy as these treatments substantially improve overall survival for women with breast cancer. Traditional prognostic factors, however, are inexact as mentioned above. Researchers at the Netherlands Cancer Institute were able to identify "good-prognosis" and "bad-prognosis" signatures based on the expression of 70 genes that was better able to predict the likelihood of metastasis development within five years for breast cancer patients Metastasis involves the spread of cancer from one organ to others throughout the body and is the principal cause of death in cancer patients. While the study at the Netherlands Cancer Institute applied to breast cancer patients only, researchers at Massachusetts Institute of Technology identified a molecular signature of metastasis that applied to adenocarcinomas in general.

Anticipating your valuable response towards the invitation.

Regards,
John George
Associate Editor
Journal of Molecular cancer