Effect of MAF amplification on treatment outcomes with adjuvant zoledronic acid in early breast cancer: a secondary analysis of the international, open-label, randomised, controlled, phase 3 AZURE (BIG 01/04) trial.

BACKGROUND: Adjuvant use of bisphosphonates can reduce the incidence of bone metastases in early breast cancer. Recurrence and survival seem to be improved only in postmenopausal patients, but the underlying mechanisms remain unclear. We investigated whether MAF amplification (a biomarker for bone metastasis) in primary tumours could predict the treatment outcomes of adjuvant zoledronic acid. METHODS: The study population included patients enrolled in the international, open-label, randomised, controlled, phase 3 AZURE trial at eligible UK sites who had stage II or III breast cancer and who gave consent for use of their primary tumour samples. Patients were randomly assigned (1:1) to receive standard adjuvant systemic therapy alone (control group) or with zoledronic acid every 3-4 weeks for six doses, then every 3-6 months until the end of 5 years. Minimisation took into account the number of involved axillary lymph nodes, clinical tumour stage, oestrogen-receptor status, type and timing of systemic therapy, menopausal status, statin use, and treating centre. The primary endpoint was disease-free survival; the secondary endpoint, invasive-disease-free survival, was the primary disease endpoint for the analysis in this report. MAF amplification was assessed by fluorescence in-situ hybridisation of two cores of breast tumour tissue in a microarray, done in a central laboratory by technicians unaware of treatment assignment. We used multivariate analyses to assess disease outcomes by intention to treat. We also assessed interactions between MAF-positive status and menopausal status on efficacy of zoledronic acid. The AZURE trial is registered with the International Standard Randomised Controlled Trial Registry, number ISRCTN79831382. FINDINGS: 1739 AZURE patients contributed primary tumour samples, of whom 865 (50%) had two assessable cores (445 in the control groups and 420 in the zoledronic acid group). 184 (21%) tumours were MAF positive (85 in the control groups and 99 in the zoledronic acid group) and the remaining tumours were MAF negative. At a median follow-up of 84·6 months (IQR 72·0-95·8), MAF status was not prognostic for invasive-disease-free survival in the control group (MAF-positive vs MAF-negative: hazard ratio [HR] 0·92, 95% CI 0·59-1·41), but was in the zoledronic acid group (0·52, 0·36-0·75). In patients with MAF-negative tumours, zoledronic acid was associated with higher invasive-disease-free survival than was control treatment (HR 0·74, 95% CI 0·56-0·98), but not in patients who had MAF-positive tumours. Additionally, among 121 patients not postmenopausal at randomisation with MAF-positive tumours, zoledronic acid was associated with lower invasive-disease-free survival (HR 2·47, 95% CI 1·23-4·97) and overall survival (2·27, 95% CI 1·04-4·93) than control treatment. INTERPRETATION: MAF status can predict likelihood of benefit from adjuvant zoledronic acid and merits further investigation as a potential companion diagnostic. FUNDING: Novartis Global and Inbiomotion.

Enhanced MAF Oncogene Expression and Breast Cancer Bone Metastasis.

BACKGROUND: There are currently no biomarkers for early breast cancer patient populations at risk of bone metastasis. Identification of mediators of bone metastasis could be of clinical interest. METHODS: A de novo unbiased screening approach based on selection of highly bone metastatic breast cancer cells in vivo was used to determine copy number aberrations (CNAs) associated with bone metastasis. The CNAs associated with bone metastasis were examined in independent primary breast cancer datasets with annotated clinical follow-up. The MAF gene encoded within the CNA associated with bone metastasis was subjected to gain and loss of function validation in breast cancer cells (MCF7, T47D, ZR-75, and 4T1), its downstream mechanism validated, and tested in clinical samples. A multivariable Cox cause-specific hazard model with competing events (death) was used to test the association between 16q23 or MAF and bone metastasis. All statistical tests were two-sided. RESULTS: 16q23 gain CNA encoding the transcription factor MAF mediates breast cancer bone metastasis through the control of PTHrP. 16q23 gain (hazard ratio (HR) for bone metastasis = 14.5, 95% confidence interval (CI) = 6.4 to 32.9, P < .001) as well as MAF overexpression (HR for bone metastasis = 2.5, 95% CI = 1.7 to 3.8, P < .001) in primary breast tumors were specifically associated with risk of metastasis to bone but not to other organs. CONCLUSIONS: These results suggest that MAF is a mediator of breast cancer bone metastasis. 16q23 gain or MAF protein overexpression in tumors may help to select patients at risk of bone relapse.