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Use of Oncotype DX Recurrence Score® (RS) reduces chemotherapy (CT) beyond treatment decisions using Ki67-based determinations of luminal A and B breast cancer subtypes: a retrospective study in the Spanish population

Date

10 Oct 2016

Session

Poster display

Presenters

Laura Garcia-Estevez

Citation

Annals of Oncology (2016) 27 (6): 43-67. 10.1093/annonc/mdw364

Authors

L. Garcia-Estevez1, E. Hernandez2, D. Acosta2, F. Lopez-Rios2, M. Prieto Pozuelo1, I. Calvo2

Author affiliations

  • 1 Medical Oncology Service, Hospital Madrid Norte San Chinarro Centro Integral Oncologico Clara Campal, 28050 - Madrid/ES
  • 2 Medical Oncology Service, Hospital Madrid Norte San Chinarro Centro Integral Oncologico Clara Campal, Madrid/ES
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Resources

Abstract 1981

Background

St Gallen guidelines recommend the use of Ki67 by IHC as a surrogate marker for luminal A and B breast cancer (BC) subtypes, such that patients (pts) with luminal B (≥ 14%) subtypes should be considered for adjuvant CT. Oncotype DX RS is a predictor of CT benefit. The aim of this study is to assess the distribution of the RS in luminal A and B BC subtypes as defined by Ki67 and to assess treatment changes based on RS.

Methods

Data were collected from 210 pts with invasive breast cancer for which Oncotype DX results and pathology data were available. Estrogen (ER) and progesterone (PR) receptor was assessed by immunostaining (cut-off 10% nuclear staining). Ki67 was assessed by IHC [high (≥14%) and low (

Results

Median age: 50 years (35-78); premenopausal status: 122 pts (58.1%). Median tumor size: 1.7 cm (2-10); Overall, 65.7% of cases had grade II tumors, and 13.3% grade III. All pts had HER2 negative tumors, 90 were luminal A and 120 luminal B. Of those with positive lymph nodes (36.7%), 51.9% had macrometastasis. Median ER value was 95 (range: 35-100) and PR 85 (0-100). Median Ki67 index was 15 (2-63) and RS 16 (1-55). Luminal A and B subtypes showed statistical differences with respect to tumor size, grade III and levels of ER and PR (p = 0.027, p 

Conclusions

A substantial number (55.8%) pts with luminal B BC subtype had a low RS, therefore preserving them from adjuvant CT treatment. According to this data, luminal subtyping by Ki67 is not always a reliable surrogate marker for receiving chemotherapy, confirming the important role of Oncotype DX in treatment decision-making.

Clinical trial identification

Legal entity responsible for the study

Comprehensive Cancer Center Clara Campal (CIOCC)

Funding

Comprehensive Cancer Center Clara Campal (CIOCC)

Disclosure

All authors have declared no conflicts of interest.

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