Abstract P1-13-14: Discordance of ER and PR status between primary and recurrent breast cancer in association with endocrine therapy
Authors: Menjak IB , Maki E , Chung C , Berman HK , McCready DR , Sridhar SS 
Published: August 2014

Background: Discordance in tumor receptor status between primary and recurrent tumors has been previously reported. Discordant ER/PR status has been used to differentiate recurrences from new primaries. We evaluated discordance rates of ER and PR expression between the primary and locoregional/contralateral recurrences and examined the relationship with adjuvant endocrine therapy (ET).

Methods: We conducted a retrospective chart review of breast cancer patients (pts) treated with lumpectomy and adjuvant locoregional radiation (RT) from 1999-2005 at the Princess Margaret Cancer Centre. Tumor recurrence was classified as locoregional recurrence (LRR) for ipsilateral breast or lymph node recurrence, contralateral disease (CD) or distant recurrence. ER and PR were assessed by immunohistochemistry; positive if &gt;10% tumor cells staining, borderline if 10% staining, and negative if &lt;10% staining. Univariate analyses were applied to determine the association of receptor discordance with age, menopausal status, tumor grade, endocrine therapy or adjuvant chemotherapy.

Results: All 441 pts had a lumpectomy with negative margins and RT, and had a median follow-up of 8.3 years. The median age at primary surgery was 57, and 67% of pts were postmenopausal. ET (tamoxifen and/or aromatase inhibitors) was initiated in 294 (84%) eligible patients. There were 24 (5.4%) pts with LRR, 20 (4.5%) pts with CD, and 28 (6.3%) with distant metastases. Nine pts with LRR also had distant disease, and 3 pts with CD also had distant disease. Among pts with LRR, 17 had ER/PR status available for comparison. Discordance rates for ER and PR were (1/17) 5.9% and (3/17) 17.6%, respectively, and the most common change was ER becoming positive, and PR becoming negative (75%). For pts with CD, 18 had ER/PR status available for comparison. Discordance rates for ER and PR were (7/18) 38.9% and (9/18) 50%, respectively. The most common change was ER becoming positive (86%), and PR becoming positive (75%). Distant disease receptor status was only available for two patients, therefore not included. The patient with LRR and discordant ER did not receive ET, while pts with LRR and discordant PR all received ET. Among patients with CD, 15% of patients with discordant ER status received ET, and 33% with discordant PR received ET. There was no statistically significant association between discordance rates in either LRR or CD groups and use of ET. Similarly, discordance rates were not associated with the other patient or tumor variables studied, or the development of distant metastases or death.

Conclusions: Discordance of ER and PR expression was low in LRR and higher in CD, where the majority of changes were from negative to positive receptor status. Receptor discordance was not associated with endocrine therapy. This study suggests that the biology of LRR and CD may be different, and re-evaluation of receptor status could lead to additional treatment options becoming available from an endocrine standpoint.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-13-14.