Immunohistochemical evaluation of hormone receptor status for predicting response to endocrine therapy in metastatic breast cancer

Abstract

BackgroundThe importance of establishing hormone receptor status of tumors for the treatment of women with hormone receptor-positive
breast cancer has been emphasized, however, there is no general agreement as to how immunohistochemical assays should be evaluated.
It is critical to evaluate hormone recptor status when considering response to endocrine therapy.

MethodsEstrogen receptor (ER) and progesterone receptor (PgR) expression was examined by immunohistochemistry using Allred’s score
for primary breast tumors from 75 metastatic breast cancer patients who received first-line treatment with endocrine therapy
(56 patients received tamoxifen, 11 patients received aromatase inhibitors, and 8 patients received LH-RH agonist or other
endocrine reagents) on relapse. Correlation between hormone receptor status and response to endocrine therapy as well as post-relapse
survival was analyzed.

ResultsThe most significant correlation between positive ER expression and response to any endocrine therapy (p=0.011) or tamoxifen only (p=0.030) occurred when the cutoff score was set at 10%. When the evaluation was based on Allred’s score (TS), a cutoff point
of TS ≧4 showed a more significant association between positive ER expression and response to all kinds of endocrine therapy
(p=0.020) or tamoxifen only (p=0.047). When evaluated at a cutoff point of 1% positive cells, there were fifteen patients with both ER- and PgR-negative
tumors, and three patients (20.0%) responded to the therapy. Patients with 1% or more ER or PgR positive cells had better
survival after relapse (p=0.0005 andp=0.0008, respectively).

ConclusionsThe proportion score alone might be enough to predict hormone responsiveness and post-relapse survival in metastatic breast
cancer. The cutoff might be set low, for example 1%, especially for metastatic disease.