The challenge of personalized cancer treatment lies in matching the most effective
therapy to the characteristics of an individual patient’s tumor. The selection
of therapy for both early-and late-stage breast cancer, as is the case for most
cancer therapy, is still largely empiric and guided by large, population-based,
randomized clinical trials. Althoughwidely adopted, this approach is inadequate for
the selection of individualized chemotherapy regimens. Estimates of benefit are
extrapolations from the effects observed in these large trials and are not necessarily
applicable to individual patients.