High progesterone receptor expression correlates to the effect of adjuvant tamoxifen in premenopausal breast cancer patients
2006 (English)In: Clinical Cancer Research, ISSN 1078-0432, Vol. 12, no 15, 4614-4618 p.Article in journal (Refereed) Published
Purpose: Tamoxifen has long been the drug of choice in adjuvant endocrine therapy of steroid hormone receptor-positive breast cancer, and it still remains important due to its well-documented beneficial effect. Hormone receptor status is often reported as "positive" or "negative" using 10% positive nuclei as a cutoff. In this study, we aimed to assess whether a further subclassification of hormone receptor status could enhance the treatment predictive value. Experimental Design: The immunohistochemical expression of estrogen receptor (ER) and progesterone receptor (PR) was quantified in tissue microarrays with tumors from 500 premenopausal breast cancer patients previously included in a randomized trial of adjuvant tamoxifen compared with an untreated control group. Results: Our findings show a gradually increasing tamoxifen effect in tumors with >10% ER-positive nuclei. However, when analyzing tamoxifen response according to various PR fractions, we found that it was primarily patients with tumors showing >75% PR-positive nuclei that responded to tamoxifen treatment, with an improved recurrence-free [relative risk, 0.42 (0.25-0.70), P = 0.001] as well as overall [relative risk, 0.49 (0.28-0.84), P = 0.010] survival. Conclusions: Adjuvant tamoxifen improved recurrence-free and overall survival for premenopausal patients with tumors showing >75% PR-positive nuclei. No effect could be shown in tumors with fewer PR-positive nuclei. The PR was a stronger predictor of treatment response than the ER. Based on these findings, we suggest the implementation of a fractioned rather than dichotomized immunohistochemical evaluation of hormone receptors in clinical practice, possibly with greater emphasis on the PR than the ER. © 2006 American Association for Cancer Research.
Place, publisher, year, edition, pages
2006. Vol. 12, no 15, 4614-4618 p.
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:liu:diva-50166DOI: 10.1158/1078-0432.CCR-06-0248OAI: oai:DiVA.org:liu-50166DiVA: diva2:271062