The majority of patients with localized breast cancer receive some form of systemic therapy. The intention of these systemic treatments (adjuvant therapy) is to kill or prevent growth of cancer cells which have escaped from the local area but have not yet grown to a size to cause local symptoms or be detectable on imaging. Systemic treatment can be given prior to local treatment (neoadjuvant therapy) which can also cause shrinkage of the primary tumour. This allows confirmation that the medication used is active against the cancer and may allow breast conservation for a lesion that would have been too large at diagnosis to allow this. The order in which systemic treatment is given does not appear to affect long-term survival. Three forms of systemic treatment are used: (1) hormonal therapy, (2) cytotoxic chemotherapy, and (3) immunotherapy directed against a specific tumour antigen.
It is not possible to predict precisely those who will develop recurrent or metastatic cancer and would therefore potentially benefit from adjuvant treatment and those who will not develop further disease who will thus not need treatment (Figures 10.1, 10.2). An estimation of the risk of further problems can be gained using established prognostic factors. Factors known to be associated with increased risk of recurrence can be weighed together with issues such as general health to provide an estimate of the risk of recurrence and allow identification of those who have the most to gain by treatment.
Internet-based resources such as Adjuvantonline from the Mayo Clinic offer estimates of patient outcome with or without various adjuvant treatments and can aid decision making by clinicians and patients. A patient with a fairly poor prognosis (A) has a reasonably large absolute benefit from adjuvant treatment while a patient with a good prognosis (B) has a little absolute benefit from adjuvant treatment although relative benefit may be similar. (Reproduced with permission.)
Graphical representation of expression of 70 genes from breast cancer specimens with relative up-regulation of gene shown as red and down-regulation as green. Those above the dotted line have a lower incidence of metastasis and appear to have different patterns of gene expression. Such gene profiles have been used to define high- and low-risk groups to aid decisions on adjuvant treatment. Traditional methods of prognostication result in treatment of a large proportion of patients, whereas this method may reduce the number of patients receiving apparently unnecessary treatment. (Source Van't Veer et al. , Nature 415:530-6 with permission.)
It is important to recognize, however, that prognostication is an inexact science. Some patients deemed to be at low risk will develop recurrence, others at high risk who do receive ...