Abstract 1347
Background
Semiquantitative inmunohistochemical (IHC) expression of progesterone receptor (PR) adds prognostic value to the current IHC-based luminal A (LA) definition, such that patients (pts) with LA (Ki67 20%) tumors can be spared from adjuvant chemotherapy (CT). Oncotype Dx® (ODX) and MammaPrint® (MP) assays have been validated as predictors of CT benefit. This study assessed the distribution of recurrence risk in LA and LB breast tumors as defined by Ki67 and PR.
Methods
A retrospective analysis was performed in 889 T1-2, N0-Nmic, M0 tumors for which ODX or MP results and local pathology data were available. Ki67 was assessed by IHC (high ≥14% and low 20%). Histological grade was defined using the Nottingham grading system.
Results
Median age 54 years (18-77). All pts had HER2 negative tumors. Median tumor size 15 mm (2-88). Three hundred (33.7%) tumors were classified as LA and 589 (66.3%) as LB. Grade 1 tumors were higher in LA (27%) than in LB (19%) pts (p
Conclusions
There is a wide distribution of recurrence risk results between LA and LB tumors defined by Ki67 and PR which confirms the important role of gene-expression assays in adjuvant decision making. Of note about half of pts with LB tumors had low recurrence risk indicating minimal benefit from adjuvant CT.
Clinical trial identification
Legal entity responsible for the study
Ministry of Health of the Community of Madrid (Spain)
Funding
Ministry of Health of the Community of Madrid (Spain)
Disclosure
S. López-Tarruella: Advisory role: Novartis, Pfizer, Celgene. Honoraria/lecturer: Novartis, Pfizer, AstraZeneca, Celgene, Roche. I. Márquez-Rodas: Advisory role: Bristol-Myers Squibb, MSD, Novartis, Roche, Pierre Fabre, Amgen and Bioncotech. M. Martin Jimenez: Holds a patent on the predictive value of the PAM50 gene profile assay. All other authors have declared no conflicts of interest.