Abstract P5-12-01: Adjuvant endocrine therapy and risk of contralateral breast cancer among a cohort of U.S. women with breast cancer

Background: The increasing incidence of estrogen receptor (ER)-positive breast cancer in the U.S. in concert with the aging population and improved survival have resulted in an increased number of women at risk of developing a second contralateral primary breast cancer. Results from randomized clinical trials have suggested a reduced risk of contralateral breast cancer among women taking tamoxifen or aromatase inhibitors. However, little is known about the duration of beneficial effects of endocrine therapy within the context of real life treatment scenarios, where gaps in treatment and varying durations of use may influence risk.

Methods: We assessed contralateral breast cancer risk associated with adjuvant tamoxifen treatment among a cohort of 7,541 women, ages 24-85 years, who were members of Kaiser Permanente (KP) Northwest or Colorado, and were diagnosed with invasive breast cancer between 1990 and 2008 and remained at risk of contralateral breast cancer for at least one year. We also assessed risk in relation to aromatase inhibitor use, though statistical power was somewhat limited due to the relatively recent introduction of aromatase inhibitors in this older cohort. Use of tamoxifen, aromatase inhibitors and other treatments was ascertained from KP prescription and medical records. Relative risks (RR) and 95% confidence intervals (CI) were estimated using multivariable Poisson regression adjusting for study site, age at and year of diagnosis, stage at diagnosis, ER status, chemotherapy, and radiotherapy.

Results: Over a median (range) of 6.3 (1.0-20.9) years of follow-up, 248 women developed contralateral breast cancer. Among patients surviving at least five years (n=4,668), 58% were prescribed tamoxifen with a median (range) duration of use of 4.2 (0.25-16.2) years. In models evaluating joint effects of tamoxifen duration and time since last use, we observed a statistically significant reduced risk of contralateral breast cancer among current tamoxifen users (RR=0.47, 95% CI: 0.30, 0.74) and among former users with 4+ years of tamoxifen (RR=0.39, 95% CI: 0.24, 0.63) as compared with women not treated with tamoxifen. Former users with 1-4 years of tamoxifen demonstrated a suggestive reduction in risk (RR=0.71, 95% CI: 0.45, 1.10), but there was no evidence of risk reduction for former users with <1 year of tamoxifen (RR=0.96, 95% CI: 0.56, 1.64). The reduced risks associated with 4+ years of tamoxifen persisted among patients surviving at least 7 years but were attenuated among those with more than 10 years since their first primary diagnosis. Aromatase inhibitor use was also associated with reduced contralateral breast cancer risk (RR=0.46, 95% CI: 0.22, 0.97). In subgroup analyses restricted to women whose first primary cancer was ER-positive (n=5,951), findings were consistent with those observed in the overall cohort.

Conclusions: Adjuvant tamoxifen and aromatase inhibitor therapy considerably reduce the risk of contralateral breast cancer. Furthermore, our data suggest that tamoxifen protects against contralateral breast cancer while women are being treated and that the protective effect appears to continue after cessation with longer durations of use.

Citation Format: Gierach GL, Curtis RE, Pfeiffer RM, Mullooly M, Hoover RN, Nyante SJ, Feigelson HS, Glass AG, Berrington de Gonzalez A. Adjuvant endocrine therapy and risk of contralateral breast cancer among a cohort of U.S. women with breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-12-01.

Targeting ADAM-17 with an inhibitory monoclonal antibody has antitumour effects in triple-negative breast cancer cells

Background:

Identification and validation of a targeted therapy for triple-negative breast cancer (TNBC), that is, breast cancers negative for oestrogen receptors, progesterone receptors and HER2 amplification, is currently one of the most urgent problems in breast cancer treatment. EGFR is one of the best-validated driver genes for TNBC. EGFR is normally activated following the release of ligands such as TGFα, mediated by the two MMP-like proteases ADAM (a disintegrin and metalloproteinase)-10 and ADAM-17. The aim of this study was to investigate the antitumour effects of a monoclonal antibody against ADAM-17 on an in vitro model of TNBC.

Methods:

We investigated an inhibitory cross-domain humanised monoclonal antibody targeting both the catalytic domain and the cysteine-rich domain of ADAM17-D1(A12) in the HCC1937 and HCC1143 cell lines.

Results:

D1(A12) was found to significantly inhibit the release of TGFα, and to decrease downstream EGFR-dependent cell signalling. D1(A12) treatment reduced proliferation in two-dimensional clonogenic assays, as well as growth in three-dimensional culture. Furthermore, D1(A12) reduced invasion of HCC1937 cells and decreased migration of HCC1143 cells. Finally, D1(A12) enhanced cell death in HCC1143 cells.

Conclusion:

Our in vitro findings suggest that targeting ADAM-17 with D1(A12) may have anticancer activity in TNBC cells.

ADAM-17: a novel therapeutic target for triple negative breast cancer

BACKGROUND

Validated targeted therapy is currently unavailable for patients with invasive breast cancer negative for oestrogen receptors, progesterone receptors and HER2 [i.e., those with triple-negative (TN) disease]. ADAM-17 is a protease involved in the activations of several ligands that bind to and promotes intracellular signalling from the EGFR/HER family of receptors.

PATIENTS AND METHODS

Expression of ADAM-17 was measured in 86 triple-negative and 96 non-triple-negative breast cancers. The ADAM-17 specific inhibitor, PF-5480090 (TMI-002, Pfizer) was tested in a panel of breast cancer cell lines for effects on functional outputs.

RESULTS

In this study we show using both Western blotting and immunohistochemistry that ADAM-17 is expressed at significantly higher levels in TN than non-TN breast cancers. Using a panel of breast cancer cell lines in culture, PF-5480090 was found to decrease release of the EGFR ligand, TGF-alpha, decrease levels of phosphorylated EGFR and block cell proliferation in a cell-type-dependent manner. Potentially important was the finding of a significant and moderately strong correlation between ADAM-17 activity and extent of proliferation inhibition by PF-5480090 (r = 0.809; p = 0.003; n = 11). Pretreatment of cell lines with PF-5480090 enhanced response to several different cytotoxic and anti-EGFR/HER agents.

CONCLUSION

It is concluded that inhibition of ADAM-17, especially in combination with chemotherapy or anti-EGFR/HER inhibitors, may be a new approach for treating breast cancer, including patients with TN disease.