What is your approach to adjuvant therapy for patients with ER negative, PR positive early stage breast cancer?

Do you use anti-hormonal therapy for these patients?

3 Answers

Mednet MemberInvited Expert

Medical Oncology · University of North Carolina

Answered on

ER-negative but PR-positive is unusual (<5%) but not unheard of, and is worth repeating receptors to make sure is accurate. Assuming confirmed, given uncertainty about the nature of these tumors, I treat them as I do ER borderline (1-9%) tumors, with endocrine therapy but some skepticism about likelihood of benefit.

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Mednet Member

Medical Oncology · MOSC Medical College Kolenchery

Answered on

Does such an entity even exist? If it does, is it because of a false negative ER or a false positive PR? Does technical aspects of IHC staining influence the results? What would be the intrinsic subtype of the tumor? If it is luminal A/B, will anti-estrogen therapy matter in such patients?

I generally do not recommend anti-estrogen therapy.

Reference: https://www.ncbi.nlm.nih.gov/pubmed/18182677

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Mednet Member

Medical Oncology · Private Practice and Digital Health

Answered on

Very small subset <5%. Some data suggests poorer prognosis for PR+/ER-. Because PR is an ER dependent protein product, we tend to be skeptic of true ER negativity, but it is possible that we may be seeing variation of expression within a tumor or technical issues.

If encountered, I would generally want to make sure we repeat testing (if core, repeat resection markers,..etc), and a way to look further would be to do oncotype testing and assess mRNA.

There might be more work that needs to be done to learn more about this subset, but I would generally recommend endocrine therapy. Particularly if ER staining is suspect, no reason to withhold.

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