Lobular Carcinoma of the Breast and Utility of Oncotype Dx®: a Retrospective Decision Impact Analysis.

Purpose: It is still relatively questioned if the benefit of Recurrent Score (RS) extends to invasive lobular carcinoma (ILC), which represents 10-15% of all invasive Breast Cancer (BC). We present the results of the lobular carcinoma subgroup of the PONDx Italy study[1]. that collected data on real-life use of the Oncotype DX® test in Italian oncological community clinical practice.

Methods: We present the results of the lobular carcinoma subgroup of the PONDx Italy study that collected data on real-life use of the Oncotype DX® test in Italian oncological community clinical practice. The study primarily evaluated the impact of the Oncotype DX assay results on physicians' treatment decisions. In the primary analysis, data from 1724 BC patients who underwent Oncotype DX testing were available from 27 reference centers located in 6 regions of Italy (Lombardia, Lazio, Emilia Romagna, Campania, Abruzzo, and Marche).

Results: Among patients with data available, 214 had ILC. In this cohort, 100 (47%) of patients with ILC had treatment recommendations for CT + HT before the availability of their RS result. After the availability of the RS result, recommendations for CT+HT decreased to 47 cases (22%).

Conclusion: the decision to opt for the Oncotype Dx test should not be based on the histology subgroup only because a small population of ER+ ILC BC patients may still attain important information from testing. Despite this information, its predictive value needs more dedicated trials to be confirmed.