282P - Analysis of Prosigna in hormone receptor-positive early-stage breast cancer cohort after 8 years of experience at a single institution

Background

Molecular signatures are recommended in HR+, HER2- early-stage breast cancer (EBC) to guide decisions for adjuvant treatment. Prosigna® is a standardized test based on the PAM50 gene signature with provides information on risk of recurrence and permits intrinsic subtype classification of tumor. The study aimed to evaluate the clinical impact of adopting Prosigna® assay after 8y.

Methods

A retrospective study of patients (pts) with ER+, HER2- EBC was carried out between 2015 and 2023 in a single center. Gene expression analysis of tumors was performed with PAM50/Prosigna® (NanoString Technologies, Seattle, WA, USA).

Results

232 pts were included. All were node-negative. The median age was 55y (32-80) and 152 (65.5%) were postmenopausal. Risk of Recurrence (ROR) risk groups were as follows: low ROR: 97 (42%); intermediate ROR: 76 (33%); high ROR: 59 (25%). Intrinsic Subtype Reclassification: According to immunohistochemistry (IHC), 102 tumors (44%) were initially classified as luminal A and 130 (56%) as luminal B. After PAM50, 144 tumors (62%) were classified as luminal A, 86 (37%) as luminal B and 2 (0.01%) as HER2-E. The discordance rate for luminal B by IHC is noteworthy. 67 (52%) were reclassified as luminal A after PAM50. Impact on decision making: Prosigna® led to a treatment decision change in 64 pts (28%). Chemotherapy (CT) was added in 36 (27%) of the 132 pts (57%) initially assigned to hormonal therapy (HT). Of 100 pts (43%) initially assigned to HT-CT, 28 pts (28%) finally received HT alone. Follow-up: With a median follow-up of 48 months and a maximum follow-up of 90 months, no recurrence of the disease has been reported.

Conclusions

The use of gene expression platforms such as Prosigna ® directly impacts treatment decision making, allowing the selection the best adjuvant treatment adapted to the de risk of recurrence, without having registered any relapse so far in our HR+, HER2- EBC and node-negative patients. In addition, it seems that the intrinsic subtype determined by Prosigna® assay cannot be replaced by IHC parameters.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

R. Lozano Mejorada: Financial Interests, Personal, Invited Speaker: Janssen, Astellas, Roche, Bayer, Ipsen, AstraZeneca; Financial Interests, Personal, Advisory Board: Janssen, Merck/Pfizer, Orion Pharma, Advanced Accelerator Applications (Novartis); Financial Interests, Personal, Other, Travel / accommodation: MSD, Sanofi; Financial Interests, Personal, Other, Travel / accommodation: BMS; Non-Financial Interests, Member: Sociedad Española de Oncología Médica. All other authors have declared no conflicts of interest.