Recent evidences suggest that zoledronate, one of the most used bisphosphonates (BPs) in the
      clinical setting for the prevention and treatment of bone metastasis in cancer patients, may
      have antitumor activity in early breast cancer. Notwithstanding some conflicting data, the
      majority of the clinical trials have shown some positive effects of BPs on patients outcome,
      reporting improved Disease Free Survival (DFS) and Overall Survival in mostly
      chemotherapy-naive premenopausal patients after a 3-year treatment with zoledronate and
      better DFS for immediate use of zoledronate in postmenopausal patients receiving adjuvant
      aromatase inhibitor treatment. Moreover, early breast cancer patients treated with
      neoadjuvant chemotherapy in combination with zoledronic acid showed better response compared
      with chemotherapy alone.

      Even though different explanations have been proposed over-time, the exact mechanism of
      action of the anti-tumor activity of BPs is still not well understood. Basically, BPs are
      mevalonate pathway inhibitors and one of the most intriguing hypothesis supporting their
      anticancer activity relies on the modulation of the mevalonate downstream metabolism.
      Biologically active mevalonate metabolites are involved in tumour cell proliferation,
      survival, invasion and metastasis. Moreover, there is evidence that selected cancer subtypes
      may present a more pronounced mevalonate activity, able of maintaining an aggressive
      phenotype. Indeed, the mevalonate pathway has deep impact on the function of YAP/TAZ,
      transcriptional regulators of tumour growth. Preclinical evidences, suggest that BPs are able
      to interfere with YAP/TAZ expression, via mevalonate pathway. This study addresses the
      clinical role of BPs in triple negative breast cancer (TNBC) patients selected by the level
      of mevalonate pathway regulation, namely the p53 expression.

      This study is a multicenter single-arm, phase II study primarily aimed at assessing the
      anti-tumor activity of pre-operative zoledronate measured through its effect on the Ki67
      proliferative surrogate biomarker, in patients with TNBC classified according to the p53
      expression (high vs low p53 expression). An high level of p53 is defined by IHC expression
      ≥30%, while a low level is defined by IHC expression <30%, as previously described. Patients
      with newly diagnosed, untreated, operable TNBC, intended to definitive breast surgery and
      suitable for pre-operative therapy will be registered using a centralized system and will
      receive a pre-operative, single administration of zoledronate (4mg i.v.), 7 days before
      definitive breast surgery . Ki67 levels will be assessed in core biopsy tumor samples
      collected at the time of diagnosis and after zoledronate treatment at the time of definitive
      surgery. Primary endpoint of the study is the proportion of responder patients, defined as
      those with at least 30% reduction in Ki67 at surgery with respect to core-biopsy analysis.
      The secondary objective of the study is to investigate the effect of zoledronate on critical
      genes/proteins related to p53 and mevalonate pathways, p53/PIN1 and YAP/TAZ, analyzed in the
      tumor tissue at the time of diagnosis (core biopsy) and at definitive surgery. The safety
      profile of zoledronate will be evaluated by the National Cancer Institute-Common Terminology
      Criteria for Adverse Events (NCI-CTCAE) scale, version 4.0 and by the occurrence of serious
      adverse reactions. The total number of patients required is forty. The overall duration of
      the project is expected to be 32 months, divided as follows: 30 months for accrual, followed
      by 2 months of follow-up after the recruitment of the last patient, aimed to collect data on
      zoledronate safety and tolerability. The primary analysis will be conducted on the PP
      population which will include all patients registered, who received the dose of study
      treatment and underwent definitive breast surgery, with no major violations of the
      eligibility criteria or during study conduction. Proportion of responder patients, defined as
      those with at least 30% reduction in Ki67 at surgery with respect to core-biopsy analysis,
      will be presented as point estimate and 95% confidence intervals (95% CIs) for each group.
      Logistic regression techniques will be used to compare groups in univariate and multivariate
      model adjusted for ECOG-PS, sex and pre- and postmenopausal status. The results of this
      project may eventually contribute to unveil novel anticancer mechanism of action of BPs and
      new therapeutic options for triple negative breast cancer.