Background: Meta-analysis of clinical trials has shown that adjuvant bisphosphonates reduce bone metastases and improve survival in postmenopausal (PM) pts1. However, we are unable to select pts most likely to benefit. To address this, the recently identified early breast cancer bone relapse biomarker, 16q23(MAF) gain (MAF+)2, was tested retrospectively in the large prospectively randomized AZURE trial3 of standard adjuvant therapy +/- zoledronic acid (ZOL) to determine the prognostic value of MAF and its potential to predict the effects of ZOL on disease outcomes.

Materials and methods: All analyses were performed with ethics approval and consent. The biomarker analysis was completed on TMAs from primary tumors. Quadruplicate cores of breast tumor tissue were arrayed across replicate TMAs. MAF+ was detected using a validated (MAF/D16Z3) FISH test (Inbiomotion SL, Barcelona, Spain). A central laboratory (Targos, Kassel, Germany) validated the assay for analytic and diagnostic performance, established acceptance criteria, included appropriate quality controls for each assay, and performed the analyses in a blinded fashion. A copy number cut-off ≥2.5 was preset for MAF+. Invasive disease free (IDFS), overall (OS) survival and time to bone metastases multivariate analyses were performed in control and ZOL pts separately. Subsequently, interactions between MAF+ and effects of ZOL on disease outcomes by menopausal status were evaluated.

Results: 1769 of the 3360 AZURE pts donated primary tumor samples. Median follow-up was 84 months. 865 pts (49%) had 2 FISH evaluable cores and were included in the analysis of which 184 (21%) had MAF+ tumors. Tumors that were MAF+ were more likely to be of higher grade, ER-ve and Her2+.

In control pts, MAF was not prognostic for IDFS or OS although there were differences in IDFS by menopause (HR for MAF-/MAF+ in PM=0.47 [95%CI 0.25-0.88]; HR in non-PM=1.58 [0.82-3.03], test for interaction (TFI) by menopause P=0.007). In ZOL pts, MAF was prognostic for IDFS (HR=0.52 [0.36-0.75] and OS (HR=0.48 [0.31-0.75]). There were insufficient bone events (19 MAF+, 73 MAF-) in this sample set to reliably assess the impact of MAF+ on relapse in bone.

In pts with MAF- tumors, ZOL was associated with improved IDFS (HR=0.74 [0.56-0.98]) and OS (HR=0.78 [0.55-1.10]). However, the effects of ZOL in MAF+ were profoundly influenced by menopausal status with possibly better outcomes in PM women (HR for IDFS=0.74 [0.35-1.58]) but clearly worse IDFS and OS outcomes in ZOL treated MAF+ pts who were non-PM (HR for IDFS 2.46 [1.23-4.92], TFI by treatment P=0.002 and HR for OS=2.27 [1.04-4.93], TFI by treatment P=0.032). The interactions between disease outcomes, ZOL use and menopause were driven largely by an association between MAF+ and an increased risk of extra-skeletal recurrence with the use of ZOL in women who were not PM.

Conclusions: Absence of MAF amplification is associated with improved disease outcomes with adjuvant ZOL. However, the use of adjuvant ZOL in women with MAF+ tumors who are not PM at the start of treatment is associated with extraskeletal spread and worse DFS and OS.

1EBCTCG Lancet 2015;386:1353–1361; 2Pavlovic M et al JNCI 2015;107(12):djv256; 3Coleman RE et al Lancet Oncol 2014;15:997-1006.

Citation Format: Coleman R, Hall A, Bell R, Cameron D, Marshall H, Jean-Mairet J, Tercero J, Rojo F, Albanell J, Gomis R. Impact of MAF gene amplification on disease recurrence and effects of adjuvant zoledronic acid in early breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-09-01.