Variability in hormone and growth factor receptor expression in primary versus recurrent, metastatic, and post-neoadjuvant breast carcinoma

The introduction of selective molecular targeted therapy, specifically tamoxifen and trastuzumab, has significantly altered the clinical behavior of breast carcinoma. Several questions remain, however, regarding potential phenotypic drifts in estrogen receptor (ER), progesterone receptor (PR), and epidermal growth factor receptor (Her-2/neu) expression between the primary and metastatic site. Whether patients should be tested for ER, PR, and Her-2/neu expression in the nodal or distant metastatic site, local recurrence and following neoadjuvant therapy, and whether this has an effect on prognosis remains elusive. A review of 45 studies addressing ER, PR, and Her-2/neu expression in lymph node metastasis, distant metastasis, local recurrence, and post-neoadjuvant therapy revealed the following average phenotypic drift in ER, PR, and Her-2/neu expression, respectively: 13.1 % (median = 10.0 %), 13.8 % (median = 16.0 %), and 7.7 % (median = 5.0 %) for lymph node metastasis; 21.8 % (median = 19.5 %), 30.8 % (median = 33.5 %), and 7.6 % (median = 6.1 %) for distant metastasis; 19.8 % (median = 13.4 %), 27.1 % (median = 28.6 %), and 6.6 % (median = 1.6 %) for local recurrence; and 12.9 % (median = 8.0 %), 32.0 % (median = 20.0 %), and 8.9 % (median = 0 %) post-neoadjuvant therapy. The above findings support the notion of re-evaluating ER, PR, and Her-2/neu expression in distant metastasis, lymph node metastasis and to a lesser extent local recurrence. The effects of neoadjuvant therapy on receptor expression are more pronounced for PR, which may have a prognostic role in therapy efficacy.