chapter  1
Pharmacogenetics of Breast Cancer: Toward the Individualization of Therapy
ByJenny C. Chang, Susan G. Hilsenbeck, Suzanne A. W. Fuqua
Pages 9

Mortality from breast cancer results from the ability of some tumors to meta-

stasize to distant sites. Selecting patients with micrometastases at diagnosis is

crucial for clinicians in deciding who should, and who should not, receive toxic

and expensive adjuvant chemotherapy to eradicate these metastatic cells.

Although many individual biomarkers were originally attractive, over the years

most have failed to become clinically useful. In addition, the management of

breast cancer has changed, with the majority of node-negative patients now

undergoing systemic adjuvant therapy because we cannot precisely determine an

individual’s risk of recurrence. A majority of node-negative patients are being

unnecessarily overtreated because if left systemically untreated, only about 25%

of node-negative patients would ever develop recurrence. There is therefore a

critical need to identify patients with sufficiently low risk of breast cancer

recurrence so as to avoid further treatment. In addition, in patients at risk of

recurrence and in need of therapy, optimal therapeutic selection is an increas-

ingly important objective. Recent developments in applying microarray tech-

nologies to breast tumor samples suggest that these new techniques may provide

for the transition of molecular biological discoveries to clinical application and

will generate clinically useful genomic profiles that more accurately predict the

long-term outcome of individual breast cancer patients.