Evaluation of Testosterone Supplementation during Anastrozole Therapy in a Breast Explant Model.
Authors: Jankovic-Karasoulos T. , Birrell S. , Cops E. , Jindal S. , Ochnik A. , Thomas M. , Tilley W. , Hickey T. 
Published: December 2010

Background: Aromatase inhibitors (AI) are currently used as first line adjuvant therapy for postmenopausal women with estrogen receptor (ER) positive breast cancer. Side effects of AI therapy, such as arthralgia, can cause significant patient discomfort leading to compliance issues. This may be exacerbated by low tissue testosterone (T), which is naturally lower post-menopause and may be decreased further following chemotherapy. T supplementation has emerged as a potential means to treat AI-associated arthralgia and has generated favourable results in a phase II clinical trial (NCT00497458). However, T replacement in breast cancer had been contraindicated until the advent of powerful 3rd generation AIs such as anastrozole. AIs are highly efficacious in blocking conversion of T to estrogen, thereby increasing the potential for 5α-reduction of T to its more active tissue form, 5α-dihydrotestosterone (DHT), which counterbalances estrogen induced proliferative effects in hormonally sensitive breast tumors1. Our objective was to test the effects of T supplementation during AI administration on tumor growth in a human breast explant system.Materials and Methods: Fresh breast tumor samples collected from 17 post-menopausal women were cut into 3 mm3 pieces, cultured for 24h on gelatine sponges submersed in culture media with 10% steroid depleted fetal calf serum and treated with vehicle (control), T (5nM) and/or AI (25ng/ml). Tissues were stained with antibodies for ER, progesterone receptor (PR), androgen receptor (AR), and Ki67, a marker of cell proliferation that has been used to predict the outcome of therapy with anastrozole2. Tissue sections were scanned using a high resolution image scanner (NanoZoomer) and the percent Ki67 positive cells was determined by counting at least 2000 cells per slide.Results: All tumor tissues were positive (&gt;30%) for ER, AR and PR, with the exception of 1 tumor that lacked PR. As expected for primary tissues, percent Ki67 positivity (mean; range) in the control was highly variable (6.45; 1-43.2). Tissue responses to T (7.9; 0.1-46), AI (6.06; 1.4-35.3), and T+AI (4.97; 0.7-26.1) were not significantly different from control (Wilcoxon signed rank test). However, the combination of T+AI showed a trend towards reduced Ki67 positivity compared to AI alone (p=0.07). In two patients T significantly increased Ki67 positivity by 2-4 fold, and in both instances this stimulatory effect of T was reduced to or below control values by treatment with AI.Discussion: Our results suggest that T supplementation during adjuvant AI therapy does not compromise AI-mediated inhibition of breast tumor growth. Indeed, combined therapy with T and AI may further enhance tumor suppression through elevation of DHT levels in the breast. This finding supports the clinical potential of T supplementation in post-menopausal women on adjuvant AI therapy to prevent or relieve AI-associated side effects.1. Peters A et al Cancer Res (In Press)2. Dowsett M et al JNCI 2007

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4089.