Abstract P1-14-05: Is there a correlation between androgen receptor (AR) expression in metastatic breast cancer (MBC) ER+/Her2- and response to anti-estrogen treatment?
Authors: Riesco Martínez MC , Hanna W , Ghorab Z , Warner E 
Published: August 2014

Background: AR expression varies significantly according to molecular breast cancer phenotype, being more common in Luminal A and B tumors where it is found in 68 to 95% of primary tumours(1) AR expression has been related to good prognostic features2 and may be lost with the appearance of metastatic disease (2), however its relationship to anti-estrogen treatment response has not been previously described. Since AR may also be a target for antiandrogen therapy for patients who have progressed on antiestrogen therapy, knowledge of which cancers are most likely to test positive for AR would be helpful.

Objectives: To correlate the rate and intensity of AR expression in ER+ / PR+ve HER2 –ve MBC tumors with response rate and duration to antiestrogen treatment.

Methods: Thirty-two patients with ER+/PR+ve, Her2-ve MBC seen in our centre since 2008 who had received endocrine treatment and had an available biopsy from any metastatic site were randomly selected. Patients who had progressed on endocrine adjuvant treatment were excluded. Immunohistochemical examination to assess AR expression was performed on the specimens of the metastatic and primary tumor if available. Pts were classified into 3 categories according to their response to anti-estrogen treatment: A)good response: 24 months(m), B) intermediate: 6-24m and C) poor response:6m.

Results: 46 samples from 32 patients (median age 55 years, range 31-90) were analyzed. Response to anti-estrogen therapy was 59% (19/32), 28% (9/32) and 12% (4/32)for categories A, B, and C respectively. Five pts (16%) had samples from both primary and at least one metastasis. AR was +ve in 100% of the 5 primary tumor samples and 90% (37/41) of the metastases. The 4 AR –ve samples were from different pts, 3 in response category A and one in C. AR expression in the primary and metastatic site was concordant in 40% (2/5) samples. Among the 5 patients with samples from more than one metastatic site 100% concordance was found when different metastatic sites from the same pt were analyzed. Intensity of AR expression was found to be strongly +ve in 85% of the samples (34/40), moderately +ve in 12,5% (5/40)and weakly +ve in 2.5% (1/40). Primary and metastatic samples expressed of pts correlated in 100% of cases. No statistically significant differences were found between the intensity of the staining and the response to hormone therapy (p = 0.387). Conclusion: The great majority (90%) of tumours of our cohort of patients with mBC ER+ and/or PR+ were also AR+. There was no correlation between response to anti-estrogen therapy and either AR expression or intensity. Response to anti-estrogen treatment cannot be used as a guide to determine which patients might be candidates for AR testing and for a trial of anti-androgen therapy.

REFERENCES

1. Moinfar F,et al.Cancer 2003.

2. Cimino-Mathews A,et al. Human Pathol 2012.

3. Ogawa Y,et al. Int J Clin Oncol 2008.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-14-05.