Suggested Citation: Balko, J., I. Mayer, M. Levy, C. Arteaga. 2015. PR (PGR).
My Cancer Genome https://www.padiracinnovation.org/content/disease/breast-cancer/pgr/?tab=0
(Updated December 7).
Last Updated: December 7, 2015
PR (PGR) in Breast Cancer
Progesterone receptor (PR) protein expression occurs in 55–58% of breast cancers (Nadji et al. 2005;
Rhodes et al. 2000).
PR (PGR) mutations are not known to be important in breast cancer.
NOTE: ER = estrogen receptor
; PR =
Testing for PR Expression in Breast Cancer
Because ER and PR expression is predictive
for response with endocrine therapy and prognostic for survival outcomes, accurate
immunohistochemistry (IHC) measurements for ER and PR expression
in breast cancer are important (Hammond et al. 2010a).
Several different methods have been used to measure PR status. Per National Comprehensive Cancer
Network (NCCN) guidelines, PR expression in invasive breast cancer or ductal carcinoma
in situ (DCIS) tumor tissue should be measured with validated IHC assays (Allred et al. 2009
The ASCO/CAP guideline recommendations for ER and PR testing by IHC in breast cancer patients
specify the following algorithm for optimal ER/PR testing (Hammond et al. 2010a
Hammond et al. 2010b
1. Positive for ER or PR if finding of ≥ 1% of tumor cell nuclei are immunoreactive.
2. Negative for ER or PR if finding of < 1% of tumor cell nuclei are immunoreactive in the
presence of evidence that the sample can express ER or PR (positive intrinsic controls are
3. Uninterpretable for ER or PR if finding that no tumor nuclei are immunoreactive and that
internal epithelial elements present in the sample or separately submitted from the same
sample lack any nuclear staining.
Suggested Citation: Balko, J., I. Mayer, M. Levy, C. Arteaga. 2013. PR (PGR) in
Breast Cancer. My Cancer Genome https://www.padiracinnovation.org/content/disease/breast-cancer/pgr/
(Updated October 11).
Last Updated: October 11, 2013
PR (PGR) Expression in Breast Cancer
|Location of mutation
|Frequency of PR expression in
||50% (Allred et
|Implications for Targeted Therapeutics
|Response to selective estrogen receptor
modulators and antagonists
||Unknown at this timea
|Response to aromatase inhibitors
||Unknown at this timeb
Progesterone receptor (PR) expression occurs in approximately half of
breast cancer tumors (Allred
et al. 2009). In patients that have ER-positive breast cancer, 83% are also
et al. 2007).
a PR expression is
associated with favorable prognosis in hormone-receptor positive breast cancer patients
(Hammond et al.
2010). In an update of a meta-analysis of trials evaluating adjuvant tamoxifen,
predictive benefit for ER but not PR was confirmed (EBCTCG 2011),
consistent with several retrospective studies (Dowsett 2005;
Dowsett 2006; Dowsett 2008;
Viale 2007; Yamashita
2006). In breast cancer patients that are ER-negative and PR-positive, a clearer
predictive role for PR status has been measured for adjuvant tamoxifen (Dowsett 2006;
b In a large prospective substudy evaluating predictive biomarkers for
adjuvant therapy with the aromatase inhibitor exemestane in comparison with tamoxifen in
breast cancer patients, PR status was demonstrated to be prognostic and not predictive (TEAM
substudy, Bartlett et
al. 2011). This is consistent with results demonstrated in restrospective studies
with the aromatase inhibitors anastazole and letrozole (Dowsett 2008;
Suggested Citation: Balko, J., I. Mayer, M. Levy, C. Arteaga. 2015. PR (PGR)
Expression in Breast Cancer. My Cancer
(Updated June 18).
Last Updated: June 18, 2015
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