OBJECTIVES : Recently a randomized double-blinded trial has shown the effectiveness and the safety using atezolizumab plus nab-paclitaxel for the treatment of patient with unresectable locally advanced or metastatic TNBC. This analysis evaluates the clinical and economical outcome of the patients positive for the PD-L1 expression tested with a qualitative immunohistochemical assay using rabbit monoclonal anti PD-L1 clone SP142.

METHODS : A decision model tree was adopted that defines the diagnostic pathway for the patients affected by BC accordingly the scenario takes into account patients previously tested for ER/PR/HER-2 status. If patients are negative to the tests mentioned above they are tested with two different immunohistochemical assays in order to evaluate the PD-L1 expression. Based on epidemiological assumptions and taking into consideration the percentage of incidence data for breast cancer in Italy, the triple negative patients likely are 5.280 of these 1.518 are in metastatic and advanced settings.

RESULTS : A total of 1.518 patients eligible for PD-L1 immunohistochemical assay in Italy were considered, of whom 40,9% were assumed to be PD-L1+ (≥1% cut off). The patients tested with PD-L1 Ventana SP142 assay following treated with atezolizumab + nab paclitaxel shows an increase of PFS and OS in according with a concordance study compared using Dako 22C3 assay.

CONCLUSIONS : The choice of a correct diagnostic strategy is crucial in order to optimize cancer therapies in the mTNBC patients that can benefit of immunotherapy. The addition to the diagnostic pathway of the Ventana PD-L1 SP142 would identify a correct number of cases PD-L1 expression (≥1% cut off), supporting the prescription of a more effective oncological therapy.